I pretty much concur with everything E Kobesky recommended. I consider the Sumiko headshell (also available as LPGear and other brands; actually sourced from Jelco) a must. In addition to the improvements he mentioned, the tonearm wrap I mentioned (Teflon pipe thread tape) will kill the midrange glare and give a more linear, relaxed presentation.
The Denon DL-110/160 carts are a nice match, especially when mounted in a Sumiko/LPGear/Jelco headshell to better match compliance to effective mass. Recent reviews indicate that the Orotofon 2M Blue is also a great match at the same price range. I upgraded my DL-160 to an Audio Technica AT150MLX when they were only $50 more than the DL-160. Now the best price I've seen on the 150 is $299 from LPGear, but it IS a significant upgrade in speed, neutrality, transparency, and inner detail.
I also have the KAB fluid damper. They're $150. I also recommend getting a tube of spindle oil and oiling up the spindle. Some probably leaks out during shipping. I found a slight but noticeable improvement in noise floor and speed smoothness when I oiled mine up.
Technics SL12x0 'tables are ridiculously well built for the money compared to the competition. You only need to update the handling of vibration and resonances to get a very nice table in the bargain.