For DV capture any of the current Mac Pros will do pretty much in their base configuration. It's recommended that you have at least 1gig of RAM per core and a separate internal HDD for storage (apps go on the main drive and everything else goes on another drive). I'm still assuming you'll use shared storage so the local storage requirements on each machine aren't a big deal. You'll also need software, a DV deck, and an external monitor (an SD broadcast monitor) to view your footage on as well as a pair of decent audio monitors (not computer speakers).
If you need to deliver an edited master on tape to a broadcaster you'll most likely need an i/o device (internal card or external box) from AJA, Blackmagic, or Matrox that will allow you to do frame accurate outputs to a higher end DV deck that has RS-422 the ability to set TC, and, preferably, SDI in/outs.
You'll probably need some other odds and ends but at it's most basic, there it pretty much is. If you plan on doing HD stuff anytime in the foreseeable future I'd recommend getting gear that does both HD and SD. If you get SD gear only now you'll have to buy everything over again when you move to HD and that's just a waste of money.
Lethal