Suggestions for New/Used amp under $3500

My System : Von Schweikert Unifield 2 speakers. Preamp outputs from a Denon 3311ci receiver. Room size is small (12x 15 x 8) but opens up into dining and kitchen. Possibility of moving into a larger space so headroom is desirable.

Planning to order a couple of amps and keep the one i like. Ability to drive center channel also would be a nice (but not mandatory). New or used does not matter.

Wondering if i can do better than Channel Islands Audio d200 mk2 monoblock pair.

Based on reviews and recommendations i have considered the following options:
- Emotivas
- Odyssey
- parasound
- butler audio
I currently have an Emo XPA-5 and used to have a Butler TDB-5150 - both are multi-channel amps. The Butler sounded very, very good with a nice, smooth sound and pretty good "grunt".

The Emo that replaced it - I needed money, sigh - is a really good amp. It has lots of drive, great bottom end, and is very punchy. It *is* a bit more sibilant than the Butler, but I'm not sure which one is "correct". The Emo demonstrated noticeable sibilance when I first got it, but it seems to have been tamed quite a bit with extended run-in. For the money, it is a *terrific* amp.

You may find that Emo's XPR series of amps are exactly what you are looking for. Or, perhaps, their XPA-1L which is a Class A design for the 1st 35 watts and then switches to AB. Since they come with a 30 day in-home trial, why not order them and see if they perform up to snuff in your system?

There is a Pass Labs X250.5 that would blow away anything you are considering.
Interesting price range to be looking in. It will also be interesting if you can do better than the CIA amps. I hope you can keep us posted on how things work out. I've always wonder how amps like the Odyssey or Emotiva would sound. I had the VS VR4SR speakers for some time with a set of the Parasound JC-1 amps and it was a very good sounding combo. I would even think you could throw Krell or Pass amps into the mix. Or the Sanders Magtech or how about the Spectron Musician III mk 2? Or Bel Canto Ref 1000 mkII (since you already know class D can sound good with the CIA amps) If I were in your shoes I would try first to get an amp with more power than the CIA just to see how the speakers and room and all respond to something with more power. Usually the more power the better only problem is the cost of more power. If you cold stand the heat I'd try and grab a Pass 250 or 350 or even Krell 400 (might be a touch over budget but they hold their value)
I have a Butler TDB-5150 that replaced a Rotel RMB1095. Pre and Pro are Emotiva USP-1 and UMC-1. Speakers are Salk HT1TL's. The Butler brought my system to an entirely new level. Soundstage depth, air around instruments, instrument decay all improved to jaw dropping levels. Frankly I'm surprised that this amp does not get more press. Huge upgrade versus the Rotel.
Call Klaus at Odyssey. You may be presently surprised.
Based on online reviews, posts and personal suggestions, the following is my assessment of audio quality (not considering other factors like price, weight, size, heat, power consumption etc)

Emotiva < Odyssey < Butler < ci audio

Not sure where parasound fits in that ordering.

The Pass Labs X250.5 may be much better but does not appear to be within budget... even in the used market.
You should be able to get the Pass lower than the one on here now and if you come up higher, you might just be in the X250.5 territory.
"Preamp outputs from a Denon 3311ci receiver."

Whoa. Stop right there. Is your priority 2-channel or home theater? If the former your first order of business is to address the preamp issue. The preamplifier section of even a decent midfi receiver will be a bottleneck for anything you're going to get out of your Unifield 2s. Better to get a good integrated amp or a separate stereo pre and amp and incorporate them into the system and let the Denon handle only the surround processing and amplifier sections for the center and surrounds for HT duty. This is easy to do and you can have the best of both worlds of a dedicated stereo system within a home theater setup. Let us know if you need more info on this, but the Denon as a pre thing is a non starter for good 2-channel sound. If stereo isn't a big deal and multichannel is your priority I think the Emotiva amps are a good option. Best of luck.

Soix is absolutely correct. Any amp will be limited in its performance by the signal feeding it from the Denon. An amp would provide more power that may improve the sound, but overall sound quality will be no better than the preamp output, regardless of the amp choice.
Hi Soix. Thanks for the suggestion. Surely would be interested in knowing more about how it feasible to do such a mix without making a incovenient mess.

my prefs:
5.1 music > stereo > movies
You hook your high-quality source for stereo music (let's say a CD player or DAC) directly to a good stereo pre or integrated amp into its normal input (if using a stereo preamp that would then be coupled to a high-quality amp), then route the front L/R channel preamp outputs on your AVR to another input on the pre/integrated amp (I used the AUX input but doesn't matter) or to the HT bypass input if the preamp has one (not necessary but very convenient to have -- more below). When you want to listen in stereo the AVR is completely out of the loop, and when you want to listen to 5.1 music/movies you choose the AUX or HT bypass input on the stereo pre and you're good to go. If you have an HT bypass the pre will pass through whatever volume levels you've set in your AVR, which makes it very convenient as all you have to do is change the input and you're done. If you don't have a HT bypass you set a "reference" volume level on your stereo preamp (I used the 12:00 position just to make it easy and repeatable) and then redo your AVR setup to set the proper volume levels. You just need to remember to adjust the preamp's volume to 12:00 every time you incorporate multichannel, and more importantly to lower the volume knob when switching back to stereo. If adjusting the volume knob isn't a big deal to you (it wasn't to me) it opens up a lot of options for a stereo pre/integrated amp as many manufacturers do not offer a HT bypass.

The limitation of this configuration is if you're after true high-quality multichannel music across all channels as you'll still be using the AVR's preamp/amp sections to run the center/surround channels. If that's important to you you'll have to pony up for a higher end preamp/processor and amplification, which can get very expensive so multichannel music would have to be VERY important to justify it. My guess is surround music will still sound very good even using your Denon, so it's up to you how much you want to spend to bring that to a higher level. A partial compromise would be to buy a good 3-channel amp so the important center channel gets fed higher quality amplification along with the front L/R, but you'd still be running that channel through the Denon's pre section.

Hope this all makes sense, and others here may have further helpful tips/strategies since I think a lot of us have done this with our systems. I probably made it sound more complicated than it really is, but let us know if any further questions.
update.. i tried the d200 mk2 from ci audio and ended up returning them. Did some A/B against my Denon receiver and found it really hard to spot any difference. I was a bit surprised but at the same time pleased.
Since the whole exercise cost me a few hundred dollars (restocking fee + return shipping), i am bit reluctant to try other amps listed here.
A couple of us tried to help you avoid wasting your time and money, but I suppose sometimes you just have to discover things for yourself. First, driving good $8000 speakers with any part of a $1200 receiver is a mismatch and a mistake. Assuming the CI amps were broken in properly, what you likely found was the preamp section of the receiver limiting whatever benefits the amps may have provided.

IMO your best bet is to buy a good used integrated amp and incorporate it into your system as I described earlier. For example, there was a Hegel H300 for sale here recently that was in your price range. I'd bet a good pile of dough that would have produced a substantial improvement. Depending on your tastes you could also look at Ayre, Pass Labs, or Musical Fidelity integrateds among others that should also work. And if they don't you could likely resell them at little or maybe even no loss.

Not to complicate this further, but I don't recall seeing what you're using as a source so that may also be an issue.

Okay, that's all I got. If you want a qualified second opinion I saw this from the Enjoy the Music review of the Unifield 2:

Mr. Von Schweikert stated from the very first that he and his staff were very people centered and that they are committed to provide advice and guidance to their customers. The instruction manual has a paragraph titled Factory Help. "If you do not achieve "goose bumps when listening then you have not found their full potential please call us for help. Customer Service phone number, 951-696-3662”.

As always, best of luck in your quest. You'll get there.
Soix is on the money. Lots of very good integrated options in your price range and you will experience a big jump up over the denon receiver.
Soix.... Actually CI Audio shipped me one of their Preamps (VPC3) when I reported lack of any significant improvements. That helped the comparison since it was easier to level match and A/B test the CI audio pre-amp + amp against the Denon by itself. It did not affect my conclusion.

Sources used: oppo bdb-80, google play music over chromcast,

Material: sacds, dvd-audio, stereophile test/sampler cds, google play streaming, some mp3 from my collection, etc.
BTW.. Thanks for your inputs.
Its not that i am having trouble getting goose bumps, i am just looking to see what improvements are feasible within that budget.
Ayre AX-7e integrated amplifier is an excellent amp in your price range. It sounds best running in balanced mode. I suggest you give it a listen.