would be a good place to start on info for turntable/cartridge setup.

http://www.vinylengine.com/phpBB2/index.php

For cartridges consider:

Audio Technica AT440MLa

Ortofon 2M Blue

If you can spend a little more the Audio Technica AT150MLX is great with the stock SL-1200 tonearm and is probably the best MM cartridge under $400.

The Onkyo TX-8255 only has a MM phono stage, so if you want to use a MC cartridge you will need an outboard phono peramp. At that price range you can get some pretty good moving magnet cartridges. There are some high output moving coil cartridges which are well regarded, Denon comes to mind.