Avoid the A880. Yamahas less expensive models took some pretty sorry short-cuts! The A1080 or higher should be fine. That said, I think you'd be fine since you are driving Klipsch which are an easy load. However, if you end up with different speakers, the A880 may fail you!
Denon generally represents the highest value for your dollar, IMHO! However, the ideal time to buy any AVR is right after the news ones come out (buy last years model, there is not often a significant difference and you generally can save 30-50%).
If you need an AVR today, you need it today, but if you have an old unit laying around to buy a few months with, wait for this years closeouts!