Newbie - Which USED Amp & Preamp for under $2500

also agree with speaker upgrade first then build system around it

Mmrump, I actually owned the B&W 601 s2 about 5-7 years ago. They were a great value buy. A little shy in the lower mids & bass(as nearly all affordable small monitors are), a tad hard in the high freqs for my taste (I prefer soft dome tweeters), but a surprisingly balanced speaker for that price range. Your 602's have the same configuration & tweeter, except a slightly larger mid-woofer, so the mid-bass/bass is probably a little better.

The collective suggestion to upgrade speakers first makes sense, but I think your B&W's are better than your amp & preamp. By that, I mean you will be better able to accurately evaluate new components through them than you will speakers through that amp & pre. Although, I think the Haflers, run at the low end of their range, may do less sonic damage than the Adcom.

At the price range you are looking at, I'd venture that it's fairly safe to say an Odyssey, McCormack, Belles, or Bryston will perform fairly well with whatever you eventually get speaker-wise. There will be differences in their overall sound, but all are extremely well made and respected designs that withstood the test of time. They are safe bets that hold their resale value, if you find one of them not to your liking. Someone else mentioned Monarchy, their SE-100 deluxe monoblocks are also an amazing value. Well worth considering unless you need a few hundred watts per channel.

Although, I think the performance/sound in preamps varies a lot more than SS amps at that price range.

BTW, are you going to stay with monitor speakers when you upgrade? How big is your room? What type of music you listen to? And how loud?

All those things will help fine tune suggestions for you.

Darkmoebius, Thanks for the advice. I've been keeping my eye out for the amps you mentioned and I don't think I would hesitate to get one if the price was right.
Based on the feedback here, I've started a search for speakers simply to get a holistic view of what I want. To answer your questions, the room is 17X13 however it has a large opening (9ft) to a dining room. I listed to jazz, 60's psychedelic, hip-hop, ambient, pop and electronic. All of my music is digital. On occasion i will push them quite hard and wake up the neighbors. I don't have space to place them out 2-3 feet from a wall, and as a result, someone recommended the Paradigm studio 60's or 100's. I can't do stands because I have a small child.

I don't have space to place them out 2-3 feet from a wall

Maybe some cornerhorns like classic Klipsch? They are big and rock hard. But get tucked into corners so they are out of the way. The only problem is that you would probably have to find some locally because they won' be an easy ship.

Here's some Speakerlab Klipschorn remakes for $800 in central, IL.

Those Paradigms are a great suggestion, too.

The Klipschorns really open up some great amp/preamp combos. They are so efficeint you can use any flea powered amp you want and drive the snot out of the Klipsch.

I think the Klipschorns driven by McIntosh gear is an incredible sound. I like the MC225 amp with the C22 pre, great combo!!