systems seems to be playing slowly, need thoughts

When you say a "jittery" sound, do you mean as in digital jitter as demonstrated on the Stereophile test CD #1? Or is it a stuttering sound? If it is the latter, I bet that it is your charming Chinese CD player. But rather than guesswork, why not just hook up a tuner or casette or mini disk or 8-track or whatevery you have laying around. If you do this and the stuttering continues, it is the amp or preamp. Either borrow a preamp, or go down to Radio Shack and buy four RCA jacks and the stereo volume pot that they carry and work up a little passive attenuator, sub it for the preamp. If the probem is still there it is the amp, if it is gone, it is the preamp. Easy, no?

I suggest that you invert absolute polarity: swap positive for negative polarity at the speaker connectors ONLY.
Some amplifiers invert polarity.
If after inverting polarity you hear faster sound, punchier bass and less sibilance, BINGO!
Good luck

I highly doubt that it's anything related to absolute polarity, as Casouza suggested. About 50 percent of recordings are made out of phase anyway and the effects, to me, do not seem to be related to tempo problems.

I'm thinking the CD player too. Ad Viridian said, try another CD player, or some other sources and see if that makes things better. Usually amps and preamps can sound poor and distorted, but not like they're playing at slow speed.