Help : Need amp as improvement over Adcom 5503

Check todays list of items and you will see a Bryston 4B amp for $675.00. 250watts into 8ohms. 400watts into 4ohms.
Dude...... Buy it. I would if I had the money.

I'm also a Thiel speaker owner who recently moved up from
an Adcom GFA-555 II amp to a McIntosh MC-150 - which is a
great amp for use with Thiel speakers. Though the MC-150
is out of your price range; you can get an older McIntosh
model MC-2200 model amp within your price range. The MC-2200
does not have the glass face plate and meters found on most
Mac amps - only an aluminum face plate with 4 LED lights.
But it is very conservatively rated at 200 watts in to 8
Ohms and should very easily handle much larger loads with no
problem. I might also add, it is also a very smooth and
detailed amp that will match well with your Thiel speakers.
I use Transparaent MusicWave speaker cables with my MC-150
and love the sound.

I have enjoyed the sound of B&K M200's and smaller Classe amps with Thiels. I think you could find both used at your price point. I suspect the Bryston 3B ST would work nicely.

Aragon 8002 dual mono amp will absolutely kill the adcom..
I have had adcom 5800s and the aragon is much more musical and can handle loads down to 2 ohms no problem...
The build quality alone on the aragon is much better than any adcom.. add a nice quality power cord and you have a super amp..
Good luck

B&K M200 Monoblocks are great theyre for sale @ audiogon for 750.oo I like B&K amps I haave 2. EX-442 and ST 1400