Vintage Amps for Thiel 1.5

I had a sumo polaris and athena (run in bypass mode mostly) on my 1.2's. They were an amazing match. Better than krell ksa 50, rowland model 1 and 5, and a couple of threshold units I cannot remember. Of course that is in my system. What was better to me in just a couple of ways was a audio research classic 60 and arc ls-1 pre I had for a little while.  A little different speaker than the 1.5. You could try the sumo polaris or andromeda or an ampzilla amp for SS. All are really good. I wanted to try a muse amp which I thought may be very good also at the time but never did.

I did a little more research and learned that Jim Thiel used Bryston amps when building and exhibiting his speakers. So even if there are more exotic or euphonic amps available, I think a Bryston 3B would be a safe pairing.

Would it be worth it to spend a little more for a 3B-ST, or is the older 3B close enough in sound?

Some more food for thought FWIW.  First, what sub are you using and have you tried crossing it over a bit higher to see if it adds that added oomph you may be looking for?

As for Bryston, obviously great amps but just because your speakers may have been in part voiced or shown with Brystons doesn't necessarily mean they'll provide specifically what you're looking for in your system and with your tastes.  Reason I mention this is that I've had Bryston amps in my system and found their bass to be very quick and tight but not as meaty down in the upper and mid bass region as some other amps.  I noticed a nice improvement in this area between the SST and SST2 models, but especially as you move back to older models you might find them not as helpful in the particular area you're trying to address  Mind you this is just a semi-educated guess from my experience, and others with more extensive Bryston experience (especially with older vs. newer Bryston iterations) may be of more help here. 

I've had a McCormack DNA 0.5 Rev A in my system forever, and I found it to be a bit meatier and more robust sounding than the Brystons down in the mid and upper bass areas so was thinking it might be a good fit for what you're looking for.  Also, there happens to be a very nice stock DNA 0.5 available here now for a little over your $500 price target.  BTW, Thiels were frequently paired with McCormack amps at shows as well. 

Again, just a little more info to chew on, and others with McCormack and/or Bryston experience may have further thoughts along these lines.  Hope this helps in some way.