I recommend you compare how these 2 receivers sound with your speakers. You should also see if you can find other comparably priced models to check out. It's all about which receiver/speaker combo sounds best to you.
Having auditioned the Denons, and being the owner of 5 Onkyo AV receivers including the NR5008 at present, and ordering an NR5009 when it comes out, I'd hve to recommend the Onkyo. Audio quality is much better with Onkyo, and generally you get more features per dollar with Onkyo over Denon.