...the table itself -- automated start/stop, USB out, belt or direct-drive, onboard preamp, that sort of thing -- and see how cheaply you can get those features. Then spend the rest of the budget upgrading the cartridge. Ortofon has the biggest range, but there are other manufacturers as well. I'd go to http://www.needledoctor.com/ and read reviews at various price points, then see if you can find whatever you like somewhere else for cheaper.

I use a 2M series Ortofon, and I like it a lot. Mine was about $250. I use an ancient turntable that I got for free with it.