The 601 lacks 2 things that the 602 has - 7 amps and auto calibration. Aside from that, I would say they are probably nearly identical. I installed a 601 for a customer not too long ago, and I have to acually say I was surprised at the quality of this unit. The amp section is solid, and sound quality is good, setup was fairly easy and was simple enough to be done via the front panel (since I had no connection for OSD).
Question #1 should have been - what speakers are you going to run? Could make a big difference in what I'd recommend.
For the average budget system, the 601 would likely be a good starting point.
At your price point, you might also take a look at the Pioneer 1015Tx, depending on what speakers you plan to drive.