First "audiophile" system, now what? Suggestions for best "bang for the buck" upgrade?


After being beguiled with mp3s and the TV AVR, I finally realized I missed having a dedicated stereo system. With a budget of $2400, here is what I put together:
  ProJect Carbon 1 w/TizoAcrylic platter and Ortofon Red cartridge,
  Hagerman Bugle2 preamp,
  Vincent V-60 tube amp,
  Martin Logan 12 speakers.
 No special wires or cables. My room is 14x19 that is open to the kitchen. Compared to what I had been hearing, this system sounds fabulous. But now I want more fabulous. So I am writing to seek help on making short term/long term plans to upgrade. Short term means the biggest improvement in sound that costs $500 or less. The long term plan could cost maybe $2-3k or more. I have read that going from Ortofon Red to Blue might be a an inexpensive but very noticeable improvement? If speakers are my weak link, then maybe Martin Logan electrostatics would be good (when my ship comes in)?
I welcome any suggestions.
128x128etwilley
Install a dedicated line before anything else. Not expensive and you could even DIY - I did. 

In my experience, cables, power cords etc. yielded subtle (if any) improvements in sound. 

Which did you try?
A quick story about speaker cable. I'm going be memory but here goes, at an audio convention a dealer was demoing a McIntosh system, I do not remember the configuration exactly. Listeners were remarking on the exquisite sound with the typical "transparency, inner detail, micro dynamics" etc. comments. The gent who had the display quietly laughed to himself as his speakers cables were modified Belden extension cords...This is not to be a diss on exotic cables, just relating a real world story...
Lots of good advise posted, but, IMHO, a very important, (and inexpensive) step has been overlooked. Make sure that your turntable/cartridge/tonearm are set up correctly. I recently helped a friend who has an old Orcle Delphi of mine with a Rega RB250 and Ortofon 2M Red. I spent an hour or so dialing it all in for him, and he called me later that day to thank me for the work, and to let me know that it was like having a whole new rig. Just sayin........