When I got my receiver, THX wasn't really a requirement. I ended up with the Pioneer VSX-84TXsi which IS THX certified. However, the reason I got it was feature to price ratio. This unit has 4 HDMI inputs and I got it from a certified reseller (IE, warranty will be honored by Pioneer) for 1079 shipped. I looked at Denon, Pioneer, and Yamaha, and for the price the Pioneer had a lot more features than the others. Yamaha doesn't even offer a 4 port HDMI solution and with Denon you have to go to their $4k receiver to get it. Since my TV only has one HDMI input, I wanted to be sure that I'd have future expandability. For me that was the deciding factor. BTW, it's a great unit and sounds awesome with my Epic 80.500 setup.
In the end it's all about what you want to spend and what features you want in your receiver. If you're happy with it, then that's all that matters.