The Quad actually only has two mic/instrument inputs. The other two are MIDI and digital inputs. It is a nice unit, though.
As Greg suggested, get the best you can afford. Just a little more money usually brings some extra feature on board that can come in handy. 
For instance, on my Akai EIEPro, I can turn on phantom power to the four mic inputs two at a time. This means I can record condenser and dynamic or ribbon mics at the same time.
M-Audio has just released a similar unit.
If you order from Sweetwater.com you can split the payments. I use this option a lot.

Thanks guys!
I just ordered the Quad Capture through Sweetwater.  This is getting exciting!  Now I just need to be patient and wait for the fedex dude to bring all the goodies to me!
 
jon

Cool! In the meantime, if you have another $20 to play with, download one of the X3 tutorial videos onto your laptop. You can study up on what you are getting, and when you get everything set up, you can watch the video on the laptop, and work along with it on your PC.
I'm pretty happy with X3 Studio. I think you'll like it.

Thanks Bob!  I've been scouring youtube and the cakewalk site for good tutorial videos.  So far I've watched several by what I call the "Voice Of God guy".  They have a kind of trance inducing effect and I don't get much from them.  Is there a particular tutorial that you find helpful?
 
Jon

I've got the SWA Complete Bundle video. It's 11 hours of material. There's a lot to cover, and he moves along at a good pace. It's broken down into chapters, with plenty of detail.
A lot of people like the Groove 3 video, but I haven't seen it yet.
Both of these have much more in depth coverage than any of the quickie videos that I have watched.

I would seriously consider adding an additional hard drive purely for your audio data.
 
OS, programs & plugins can be installed on your C drive