Tonearm suggestions for a Micro Seiki DDX-1000

Well as of right now I've got an Audio Dynamics Corporation tonearm that was bought at the time of purchase with the DDX by it's previous owner along with an Empire MC20 cartridge. Cartridge sounds OK but I'm not happy with the tonearm at all.
I'm pretty limited to 600 at the moment as I'm shopping for a pre-amp and speakers as well. Thank you both for your input.

A Micro Seiki MA-505 will work. Used they run about $500 or so. As Raul said whatever you get will need a cartridge that matches up with the arm. I used a Dynavector 20XL on my MA-505.

Pardon the ignorance, but will I need any additional equipment for a moving coil cartridge?

If you're talking about a low output MC, you'll need a step-up to boost the signal before going into your phono stage. What cartridge are you planning to use?

Currently have the Sumiko Blue Point but wouldn't mind trying something different.