Upgrade My Turntable - How Much Do I Need to Spend?

I have recently fallen in love with listening to vinyl on my turntable.  In recent years, I have spent most of my listening time with digital music stored on my server (flac files recorded from CD's), but recently I discovered the beauty of placing an album on the turntable and listening to the entire album.  It's been a wonderful find for me.

My 2-channel room features:

• McIntosh C260 Tube Preamp
• McIntosh MC452 Solid State Amp
• Martin Logan Montis speakers
• Various upgraded cables and wires
• Acoustically treated listening room
• Pro-Ject Debut Carbon DC turntable
• Ortofon Blue Cartridge

My question is:  how big of a step up do I need to make with my turntable to take full advantage of the other components in my system?  I do not intend to do further upgrades with my speakers or amp system, but I would like to step up my game from the introductory level turntable that I bought years ago.  

I've been doing lots of reading and studying, but I would love to hear advice from some of the analog experts on this forum.  (Please don't flame my current system - there are reasons I love my McIntosh and those components are not going anywhere!)  Should I make a move to a $4000 turntable?  Or????  I would love to find a lightly used Rega RP10, and call my search over - but what do others think?

One thing that I believe I value is a simple setup.  I have read horror stories about how much time and frustration can go into getting a turntable setup and then constantly having to tinker for optimal performance.  I don't see myself enjoying that part of the process.

Thanks!