You should try to do some in store listening test between receivers and separates and see if you hear a difference. Many people claim there will be little or no difference in sound quality.
Since you can get the very nice Denon 3805 at cost, you would probably be unwise to pay retail for separates. If you find the Denon lacking in power, you could always add an outboard amp - using the Denon as a processor and possibly the amp section to drive your surrounds.