FYI, DTS Neo:6 Mode software can generate a center channel from a stereo recording. DTS Neo:6 is available in some Oppo universal players, and apparently is available in some AVRs. I'm not generally in favor of DSPs "mucking around" with my music, but you might consider DTS Neo:6 if your main speakers are relatively far apart (considering how far your seating position is from the speakers).
Separately, my understanding is that some of the vintage vacuum tube amps are capable of deriving a center channel - though I've never tried this.