ProCenter 1000 - $219
ProCenter 2000 - $349
Mythos Three - $249
Mythos Seven - $399
Mythos XTR-40 - <$400 on Ebay, could live without warranty
I would probably go with the Mythos Seven first, then the Mythos three as my second choice. I would ignore the The XTR 40, it is an ultra thin wall speaker which I suspect sacrifices sound quality for thinness, and the pro centers go to their satellite systems (unless the rest of your system is the ProCinema 1000 or 2000, if so go with the pro center speakers).
HT: PSA dual V3600's - PSA MTM-210T L/R - PSA MTM-210 Center- PSA 110sr Surrounds - Denon 3313CI - Sony BDP-S5200 - Panamax M4300 - Direct TV - Apple TV - Xbox360
Living Room: PSA XV15se - PSB Image T5 L/R - PSB Image B5 Center - Marantz SR5006 - Panasonic BDT210 - Panamax M4300 - Direct TV - Apple TV - Sony Wii