Thanks for the suggestions, everyone. They were a good basis for research, but the more I look, the more options open up. I'm having trouble deciding which product to purchase.
My friend and I are fans of Tracktion software, though we've only used the demo (fully functional except it makes occasional watermark hissing noises in your output.) I discovered that the franchise (now Tracktion 2) is owned by Mackie, a most reputable brand-name for audio. They have Tracktion + hardware bundles. The cheapest product is the "Spike." It has a USB 1.1 interface and some customer reviews complain that they have issues with latency. I suspect that there is probably a CPU element to this, however. I was wondering if USB is viable for low-latency recording if you have a good CPU, or is firewire the way to go for external devices? Mackie's second-cheapest bundle is $700, breaking the bank.

If you're relying on USB as your connection from your interface to your CPU, expect some latency...even at USB 2.0. Heck, even Firewire still pops with an occasional latent spike. A few things come into play when dealing with latency and there are ways of combating it, but the USB connection is your bottleneck ultimately, regardless of CPU speed. Shoot for firewire if possible, but the latency may not matter as much on your system. Hard to tell until you get it attached to your setup.

I've heard good things about Tracktion, that it's actually pretty easy to use. They try and put the entire interface on one screen. I'm not familiar with it's limitations track wise or "voice" wise. It may be the way to go if you can produce decent results with it while demo'ing it.

Good luck!

Thanks again, everyone, for the recommendations. If anyone's interested, I'm now the owner of the Focusrite Saffire LE. I got this one because it is nearly the same as the regular Saffire (minus Cubase LE and some hardware features that I wasn't going to use). This left room in the budget to get Tracktion. The Saffire LE seems to work great so far. I don't have anything really nice for monitering yet but I can already tell that the frequency response is much better than my on-board sound. Also the sound coming in is not distorted and the Latency is only 10 ms.