Would a Pass Aleph 5 be able to drive Thiel 3.5 ?

The Pass Aleph series are all single ended. That topology cannot operate in anything other than class A (and still be listenable!).

Get a used Plinius SA-100 and end your search ($1800 to $2100 depending on the condition). The Aleph 5,Bryston 3B, or 4B-ST will not have enough current to drive the Thiel CS 3.5.

With all due respect to Audiomax while the Pinius SA-100 might be a good choice with the Thiel CS 3.5's I don't think that the two Bryston amps lack the current any more so than the Plinius might. All would be at the very least adequate. In fact the Bryston 3B is probably very very close to the Plinius in this regard. I'm not so sure about the Aleph 5, but my guess would be that it too can handle the load.

I currently own Theil 2.3's and a Pass Labs x-250(synergy):) I have listened to most of the Thiel line up past and present. Before upgrading to the x-250 I was using x-150 again synergy. When auditioning the 2.3's I compared the aleph 2's vs the x-150. I personally preferred the x-150's. The x-150's goto 15 watts in class A mode. The x-250's goto 40 watts in Class A mode. The smaller amps I compared them to were absolutely terrible; not enough power. Now my Thiel's sing:0 Also owned the x-2 preamp and it is 90% of the x-1 which I know own.

At low level volumes I think it would, but i would opt for a higher power amp. Classe are know to be good matches with the Thiels like the CA 201.