If you're happy with the performance that your hardware puts out, I don't see any reason to upgrade for sake of upgrading. The big 'upgrade' I would look into is your room. How are the acoustics, and have you done anything to treat any deficiencies?

In my experience, the room makes just as big a difference as the speakers in defining the "personality" of your audio system. IMO, it's more crucial than the digital front end components, amplification, cabling, etc. Only the speakers and analog front end components have an equivalent amount of variation to account for.

If you prefer to stick with hardware upgrades, I would either save up for the speakers or invest a portion of your budget on a cartridge upgrade (IMO, the most overlooked component with an analog setup). The cartridge really defines how your vinyl sounds, more so than the turntable and tonearm (of course, a crappy turntable/tonearm will sound lousy no matter what cartridge you put on it, but even an entry level turntable/tonearm can perform very well with a decent cartridge).