I have the VGT's, but I haven't ever heard the the P363's so I cannot comment on them. I'll tell you that I have multiple stereo setups and the VGT's are the best sounding of all of them. I do have them X'ed over at 80Hz to subs, but nothing I have throws up the huge soundstage and images like the VGT's. I can also tell you that source material plays a big role in how they sound as the poorly recorded stuff sounds well, poorly recorded.
I first had my VGT's bi-amped from an Onkyo 809, but later added an Emotiva XPA-3. The only difference I could tell between the two was the bass was a slight bit better with the XPA-3 when I was running them full range, so I highly doubt your Denon is the problem. Your room is almost twice as wide, but the same length as the one I have mine setup in. I too have a door sized opening as well.
I have mine setup as an equilateral triange with my seating position and I feel they sound best this way as I have tried sitting further back and closer before. I also have them toed-in so they line up with my corresponding ears. I absolutely despise Audyssey when listening to music, but YMMV.
I have also spent enough time with my setup to know it sounds differently depending on my mood, what time of day it is and how distracted I am when I listen. In the dark, with the ambient noise level low and closed eyes is when the VGT experience can be transcending for me. I would heed Gene's advice and spend a week or so listening to each pair by themselves with different types of material and go from there.