What Turntable to buy under $600 ?

I agree with the last fellow's assessment of the response provided to date. Really going off the mark.

I would, however, bet my ears and wallet on the Sota Sapphire. I have owned several Sota's (still own a Star Sapphire and absolutely love it), classic Micro Seiki, MusicHall MMF7, and one or two others. SOTA!!! Try reaching just a little further and pick up a good used Sota Star Sapphire (vacuum). I can't imagine you'd be disappointed. If it needs a tweek or a part Donna at Sota is wonderful to work with.

OK. The Rega P3 will fit my needs, but what about a matching (quality and cost-effective) MM cartridge to mate with the TT?

I use a Goldring 1042 with my rega. It's quite fiddly to align due to the stylus profile, but sounds very good, and is an excellent match with the table. I think there's a dealer selling them at a special price on audiogon if you search for goldring, or go to www.mantra-audio.co.uk and buy direct from the UK ... it's much cheaper than buying from a US dealer.

I have also used Rega Super Bias, which is quite pleasant, but not as good as the Goldring.

Many in the UK seem to like the Denon DL110 and DL160 high output moving coil cartridges, though I've not heard one myself. These MC cartridges work into most MM input stages. They're inexpensive and can be found at needle doctor.