T., welcome. It's difficult sometimes to use words to describe a sonic impression, and it's uncertain what the "small" sound of the VP-100 really means. Is it possibly just a matter of level calibration that increasing the center channel by a dB or two with the 3803 would help? The VP-150 is said to have somewhat wider dispersion for off-axis listening, but this may have nothing to do with what you're talking about. It also is said to have a somewhat higher ultimate output capacity, but the VP-100 should have plenty for your listening distance and room size. So, I'm inclined to doubt that you need the 150. As I said, try increasing the center channel level if you haven't already experimented with that.
So far as a receiver for your new setup, there're several excellent ones in your price range, and I'll especially bring to your attention the HK635 which is offered by J&R Music at a very good price of a little under $700 with shipping included.
I'll also throw in for free a comment on your "as intended", relating to playing CDs in two channel. We shouldn't be confined to the limits of the format if we have the capability to reproduce it with a little more realism by extracting the ambience naturally present to various extents in the two channels and playing it from surround speakers, where it belongs. Using processes such as DPLII, Logic 7 and Neo:6 can often help, depending on how much reflected ambience is present in the recording.
