Yamaha RX-V757 with Klipsch F2 speakers

Maybe you could try it out for a few days?

Both of those components you are refering to are likely on the bright and analytical side (Refering to the Yamaha from past experience). I would NOT mate them together personally, as they don't compliment each other well(speakers/receiver). I'd go with a warmer more forgiving sounding receiver in the Denon if you already own those Klipsch speakers. The old Synergy series speakers weren't as bright and hollow as the newer series, FYI. I know, I've owned and compared em both.
Also, the new Denon's have an INDISPENSIBLE Audyssey MultEQ system that's superb, and much better/more effective than the Yamie's.

I don't know too much about the F2 but I use the rx-v757 with Klipsch ChorusII and Quartets before that. The yahama is a great HT receiver and very easy to setup but I use it for 2 channel listening as well. For fun, I've used my laptop as a source to it via a toslink cable to listen to mp3's. I have read that the yamaha's are bright too but I don't notice it in my setup. But see if you can try it before you buy - it's the best way to find out if it works for you.