Threshold, Parasound, Pass Labs or Nakamichi?

I have a question regarding my Arcam AVR350 and adding an amp.

I have been a novice hobbyist for over 20 years and have enjoyed the sound of a Nakamichi TA-2A, Adcom GCD-600 and 700, Nakamichi cassette deck and a number of KEF speakers. First and foremost, I am a diehard KEF fan. I have listened to various B&W 800 series, Wilson Audio and KEF Reference and have recently acquired a pair of KEF Reference 205/2s. I initially hooked them up to my little Nakamichi and loved the sound but obviously needed more power and needed to step up.

Unfortunately I also wanted the convenience of running my TV, DVD, and cable as well as my CD player and tape deck. I consider myself an amateur audiophile who loves music first and wants a home theater second. After a year of research, I found the Arcam AVRs were reviewed as the "best" receiver for sound. I acquired the AVR350 and was surprised. This may sound ridiculous but my 50 watt Nak seemed to produce a fuller and more 3 dimensional soundstage than the 120 watt, in stereo, Arcam. I do realize amps drive the speaker and am unsure of how many amps either of these units produce. I love the simplicity of the Arcam, the ease of use and what it does. However, the music sounds very accurate but "flat". The sound is much more 2 dimensional to me. The bass is significantly less pronounced with the Arcam also. I actually enjoyed the sound of my Nak better.

Hence, my question. I am considering purchasing a used amp and hoping to have the convenience of the Arcam pre-amp with the warmth, body, imaging and soundstage of a better amp. Obviously I am a fan of Nelson Pass's technologies and I am sure my dream system would consist of Pass Labs monos. Realistically, I am wondering if anyone would recommend any of the above amps based on their experience. I am considering a Nakamichi PA-7, Threshold s500 or s500e if I can find one, Parasound HCA3500 and I think my budget is still out of reach of a Pass Labs used amp.
One additional note: the Nakamichi actually produced higher volume levels than the Arcam. This really surprised me and leads me to believe that I definitely need an amp with high current.
Threshold T-200 would be nice but rarely come up for sale nowadays...
You would like an Eagle 2a, b, or c, or Eagle 4... very nice high current amp underpriced also
The Forte Model 3 is a very nice amp. It sells on Agon for $400-500. I drive my Apogee Divas with them.
If you find yourself unable to get the stasis gear, though Pas, and Nak have served me quite well; I'd also say to look at dual mono (same box or two box) AAragon (8008 or Palladium) amps.
It also depends what Pas you like. The Alephs I've owned are said to be sweeter than some of the later bigger amps. I've also heard that Classe can do well when Pas is not budget.
Not sure about Classe. I have had Classe CAP-100 integrated. Great soundstage, but complete lack of bass. The Nakamichi TA-4A that is in my main rig now has TONS of bass and great soundstage too.
Try the Adcom GFA5500. I've owned 2 & they sounded very good, to me. Around $500.00 used and 200 watts per channel.
This is a realistic match for your Arcam receiver/preamp.
I believe it's a Nelson Pass design, too.
Nelson Pass seemingly had zero to do with my beloved Forte' Model 55 (maybe the last thing Forte' made...well after Pass left Threshold), but I think his vibe is in there anyway as it is a GREAT amp for the $400 I paid last year...maybe I can get Pass to sign it for me or wave his hands over it. Also, Adcom amps have served me well so I can second that suggestion...the Mosfet versions can be killer for the money.
I was using a Nak PA-5 and a PA-5 for many years. Then I purchased a Threshold 400a and swapped it in. I am not familiar with comparable Threshold amps the 400a (updated) totally killed those Nak amps. I now know what the is meant by muddy sound and those Nak amps sounded muddy compared to the 400a.

I was shocked at how much better the 400a sounded.
I like my classe ca-150 quite a bit fwiw. I'd actually like to get another one some day so I can run them bridged. I had an adcom 545 before and the classe was quite a step up; more bass, fuller sound with good detail.
I would first beg/borrow an amplifier from someone and try this to make sure the preamp section is not the culprit.