buget used amp ?

I would like to find a nice budget amp to compliment an Adcom GTP-500ii, the amp will be power Thiel cs 1.6.  The Pre Amp and Speakers will not be replaced.  Thoughts? Thank you.
I think it’s a bit of a shame to drive your excellent speakers with a $500 amp, but to each his own.  There’s a Bel Canto S300 available here for $750 that at least won’t offend your Thiels.  Best of luck. 
I would go with a B&K stereo 202plus, an adcom gfa 555 series 2, or a parasound hca 3500 for your thiels because the thiel speakers need some power to get a full sound out of them and all these amps will do that some more than others but all are quite capable performers.
I've been using a NAD 2100 with my Adcom GP555 ii preamp to power my Theil CS1 speakers for over 30 years with no problems.  I think you can find one for around $200. The more power the better though.
This won't be a popular recommendation but a practical one, try a Crown 1500, 525 watts at $450 new. I used one with ACI speakers, have A21 now with my Maggie's. Your speakers need power and you are on a budget. 
I would add Parasound HCA 2200 mk2 to the list.
Also, there is PAS 2002PCA, sold new by thomannmusic.
It’s a PA amp, speakon and xlr connections only, still I tried it on the account of the positive user reviews, and I kept it. Not as powerful and warm (excessively warm?) sounding as HCA 2200 2, still a very capable amp (NB: it’s got no feet, and it’s bright blue).