This is one place we differ in opinion; I've found that with a lot of soundtracks the center channel has a lot of specific dialogue information. When I use a 2.1 or 4.1 setup, the processor sends the center channel information to the main speakers, producing a Phantom Center. Two problems arise with this:
1. This Phantom Center works best for an ideal listening position centered between the speakers. In an environment such as my own where viewers are not ideally centered it can lose focus.
2. With the dialogue channel mixed into the mains the balance can be almost unlistenable. The volume necessary to hear volume becomes deafening when effects come in.
I would argue that if I had a rig that was solely used for HT and had to make sacrifices, I would rather have a high quality center channel alone rather than two mains and no center channel.
I'd like to thank you for your help and guidance. You've help me focus some of my thinking. I'm left now with assessing what I have and choosing the elements which will best fit into the HT/Audio system in the living room. I was originally thinking of an all-Omega 5.1 setup, but the physical size makes that impractical in my 15' (w) x 22' (l) x 13' (h) room. I've pretty much narrowed down to keeping my Audioengine P4's in the surround and height channel positions. They are small(ish) and can be wall-mounted among the wall art with minimal visual impact on the room. The center channel will be a unique implementation of the RS5 1.5 way, horizontally positioned. Subs are being completed but are 8" Peerless paper drivers in sealed enclosures and will probably be connected at speaker level to the L/R mains. My last remaining decision is whether to use Super Alnico Monitors or RS5-based speakers for the L/R mains. The SA's would theoretically be the "better" speaker, but would not fit as well physically and would not be a 100% match to the center. The 1.5 way RS5 would be an identical tonal match to the other center speaker and would offer an additional 3 dB or so efficiency. The last point may be important since I will likely use my 4wpc 421a amp as the two-channel amp for this system. 97.5 dB vs. 93 (or 95, depending on what spec Louis gives you) dB is easier to drive. And since my amp has OPT's with 4, 8, and 16 ohm taps I can tailor it to a lower impedance. The SA's can serve as alternate speakers in the dedicated room, or if space becomes a real issue find their way into a new, loving home.