Upgrading: What to use with Dynaudio 3.3's?

I auditioned a pair of Dynaudio 3.3's and they sounded fantastic, so I then purchased a pair. Hooked them up to my Adcom GFA5800 and old Marantz preamp and the speakers sounded good. Then hooked them up to my Yamaha home theater receiver (it serves it's purpose) and the Dynaudio's sound worse than the Boston Acoustics AV70's I have attached to the Yamaha daily. The highs from the Boston's were better, the mids were more open and the Boston's just sounded better. A bit disheartened, I've decided I need a new amp and preamp for the Dynaudio's. I'd like to be able to use them for HT and stereo in the future, but I'm thinking a 5-channel amp and processor for the HT and still have excellent sound for stereo isn't in the budget, so I'll do it one step at a time. Perhaps get a good two-channel and a preamp with HT passthrough and add the three channel and processor later? Is this a good approach? I've read the Dynaudio's need lots of power - does anyone have any experience?
I'm thinking of an amp that can be had used for around $1500-$2000 and a preamp that is in the $1500 range.
Two questions in addition to the ones above:
What's the best bang for the buck?
What works well with the Dynaudio's regardless of price?

I had an analogous situation. I have Dynaudio Gemini speakers, which aren't quite as nice as the 3.3's. I haven't heard the 3.3's, but here is my experience with the Gemini's:

I first used my speakers with a Harman Kardon PA-5800 amp (80 watts/channel) and a Lexicon CP-3 (I was experimenting with the idea of a music surround set-up), and also with an old NAD 7100 receiver (60 watts/channel). I also tried the Dynaudios with my main home theater set-up, which consists of a Lexicon DC-2 and a Marantz 5 channel amp (170 watts/channel)(I A-B'd the Dynaudios in 2 channel mode with a pair of M&K S-100Bs). I was disappointed with the sound of the Dynaudios with these setups. The bass was muddy and the midrange wasn't "there" (but the tweeters produced excellent highs).

I then got a Musical Fidelity A-300 integrated amp (150/channel). The Dynaudios really came alive. The bass is much tighter and the midrange is lush. The tweeter is the best that I have heard in my limited experience. The sound is musical, yet detailed in a way that is not clinical sounding. (I sound like a hoity-toity reviewer): )

I'm very pleased with the Dynaudios and have given up the upgrade bug. (for now): )

Given the above, I suspect that an upgrade in any of your equipment will produce an improvement in sound. The problem is not with your speakers, IMO. And, the problem is not necessarily with the amount of watts generated by your amp. My 150 watts/channel MF sounds better than my 170/channel Marantz (albeit with different pre-amps). It's the quality of the watts, not the amount, IMO. I haven't heard the Adcom GFA-5800, so I can't say if another amp will make a big difference for you.

In your price range, you should consider a Musical Fidelity amp/pre-amp/integrated amp. JMHO. This is just based on my own experience.

Perhaps the MF sounds good to me with my Dynaudios because it is does not have as much of a "digital character" as my other equipment. As I think it through, you might want to look at tube equipment or tube-sounding equipment like the MF. I'm sure that there are several excellent choices in your price range. Maybe you can use your $3500 budget and get a BAT amp, or another fine tube amp, and live with the Marantz for a while. Good luck!
I'm using Mark Levinson 380s pre., and a Mark Levinson 23.5 Amp. with the ones i have and they make very good music IMO
Audition a BAT 6200 amp. You can but a 2 channel version and get a multichannel version when you do the HT thing. Dynaudio's need high current amps to sing.

Have Fun.
I was looking for a power amp for a pair of Dynaudio Contour 1.8 speakers about 2 years ago. I tried a Musical Fidelity A3CR, Parasound HCA-3500, Audio Research D-200, BAT VK-200, Krell KAV-500 and a Krell KSA-100S. The key thing learnt was that the speakers require a lot of current besides a lot of power. The MF, AR and BAT did sound good but they were underpowered. The Parasound was powerful but sounded bad. The KAV-500 matched best in terms of power and current, but the KSA-100S was best balancing power and musicality.

Tube amps are not the right ones for the 3.3s.

For your stated budget, consider an Audible Illusions Modulus 3A preamp for around $1000 used, Bryston 4BST amp around $1300 used and $300 for a pair of Transparent Music Wave Plus speaker cables.

Your problem with the Yamaha was that the 3.3s revealed the shortcomings of the receiver while the Boston Acoustics did not.
I've had Dynaudio's mated with AVA gear and they drove them to perfection. You can get the Transcendence 7 pre-amp and Fet-Valve 550 EX amp for your stated budget, new. I doubt you'll find anything more dynamic in your price range.
I previously had the Dynaudio Contour 3.3 speakers and had them hooked up to the Conrad Johnson 2500A (solid state 240 into 8) and they sounded quite good. Other combinations that were successful for me were the Simaudio Amps and Musical Fidelity Integrated Amps.
To my ears, in a small room the Audio by Van Alstine 350Ex amp is perfect with my 1.3SE Dynaudios. It drives them astonishingly well. Dynaudios are hyper current suckers, and the AVA gives them what they ask for. I have also listened to it with 3.0, doing a very musical, dynamic and detailed combo.
As you have the 3.3 model, I suppose your room is big, so you should go with 550Ex if you want loud volumes.
Within your budget, you can buy an AVA 550Ex new, and they have a 30 day return policy.
About preamps, the transcendence 7EC has a HT bypass for HT processors. You should give them a listen.
Hope this helps
A friend of mine has the 3.3. At his house he had an Aragon 4004 mated to a YBA pre. Very nice. Then he hooked up the YBA to his Clayton M100's. What a difference. The speaker came to life. The Aragon sounded thin and lifeless compared to the Clayton. I was dramatically impressed. He did say he had to play with cables for awhile to get the sound right. He bought the Clayton used but I don't know what he paid.
Thanks everyone for all your thoughts and imput so far!

Do you think I'm on the right track wanting a preamp that can do HT passthrough, or should I stick with a two-channel system and upgrade the preamp and get a 3-channel amp at a later date?

I guess high-current is requirement for the speakers. What about McCormack or Classe?

For anyone who has listened or owned the 3.3's... how would you classify their sound? Bright? Forward mids? Recessed lows? Component matching is key, and while I plan on demo'ing gear, I don't want to waste time going down the wrong path.