preamp- Mac C2300 tube and has built in phonoIt's very hard to believe you have the system(s) listed above, but you don't have basic answers already to the beginner-level turntable/vinyl question you're asking! You're either pulling our collective leg, or else you've inherited these components, right?
Krell MCX 350 monos and PBN Audio KAS speakers
Mac MC275 tube amp and Klipschorn speakers with Volti upgrades
But if you're sincere, and those are your system components, I'd say budget minimum $15,000 for turntable, tonearm, cartridge, phono stage (better than Mac built-in), cable, set-up