best upgrades?

I recently bought my first TT and now I am hooked. The problem is now I have the bug to start upgrading everything. I am looking for advice on what pieces provide the biggest change in sound. For buying a $2500 cartridge better than buying a $2500 phono preamp? In short, what are the best bang for the buck upgrades in Vinyl listening.
Lots and lots of LP's. The hardware can wait. :-) But, if you must the cartride should come first, providing that it is suitable for your arm, and next come the phono preamp. Great cartridge into a poor phono stage = garbage, poor cartridge into a great phone stage = garbage. You've got to get the match of the cartridge and phono stage right, within your budget of course.
I doubt anyone can give a suitable recommendation without first knowing what you have to begin with. Can you list out your playback system first?