I guess it depends on what kind of play you want to get into.
For woodsball:
there is no reason to spend too much money, on a paintball marker, to play woodsball. You would be fine something along the lines of a Tippmann 98C, or Tippmann A-5, or even a Spyder, and Ion. All of those markers can be run off of Compressed air or CO2.
For Speedball:
If you wanted to buy a tippmann for speedball, I would recommend the A-5 with E-trigger. Other's include the Smart Parts ION, and the Indian Creek Design (ICD) Promaster (
http://www.icdpaintball.com/icd05/intro.asp ). The Promaster I think runs $300-$400? I don't really remember. I'm not a big fan of Spyders. Also, you could look at the Bob Long Defiant, which I don't think is too expensive. And you could always buy a used high end marker. you can find some nice one's for pretty cheap.
But, like I always say, check out your local paintball proshop. Those guys tend to know a lot and need all the support they can get. They will definately be able to help you out first hand.