You mean using a HTPC as a Pre-Pro and connect to an External Amp via analog outputs?
Well, it should definitely do everything that a $5K Denon Receiver can do.
Actually, it should do even MORE with all those software outthere.
For example, PowerDVD 8 & 9 has MLP-decoders for DVD-Audio playback and my AVR-5308CI can't do that.
The HTPC should have audio decoders for DTS-HD MA and TrueHD and 1080p Video Upscaler.
Wait, can you make it 4K-Video "ready" for when it comes out?
Definitely needs to have WiFi for Internet Radio, etc., and Tuners for Radio and HDTV, etc.