Which one? Theta Intrepid 100w/chx5 vs Cary5 200w/

Neither one - get the Butler Audio TDB-5150 and revel in the glory of TUBES (driver stage).

I was wrong! I have myself replaced Theta Intrepid with cary Cinema 5 (for center and 4 surrounds). The Cary Cinema 5 is a lot better !!

I believe the Intrepid is better sounding

I'd go with the Cary in a heartbeat...It's without peer in the 5 channel amp category regardless of price.

I have noticed in my system that the speakers sound better with more power behind them. I have used the EAD Powermaster 2000 (400 watts/channel) and the CAL MCA 2500 (500 watts/channel) to drive speakers rated at 50 to 200 watts. Both are reasonable on the used market but neither company exist anymore. The speakers produced music which was fuller and more detailed with out having to crank it up. Both amps that you mentioned have great sound but if you like the extra power go with the Cary.
It could also depend on your speakers and their synergy with the amp.
Good luck.