Ahh, see, now I understand your question. You need the following:
1. A Digital/Analog converter. The RME Hammerfall series is nice, but expensive. The Echo Indigo I/O card sounds like it might be up your alley. Of course, it's only two channels. There are many, many other options. It's a popular field. You may want to check out M-Audio's web site, they have a lot of options at quite reasonable prices (<$200) for prosumer-level work.
2. A MIDI controller and/or breakout box. If you're into MIDI, that is.
3. An external hard drive. If you want to have the fewest problems, this is the way to go. USB or Firewire, your choice. I personally recommend firewire, as it has an edge in throughput for storage devices over USB. On the other hand, USB has a whole lot of options for I/O.
The one I'm saving my money for is the M-Audio Ozonic. http://www.m-audio.com/products/en_us/Ozonic-main.html
. MSRP $599.95, you can pick it up off of eBay new (it's a brand-new product, so there are few if any used ones) for about $100.00 off. Chief benefits:
* 4-channel audio I/O (equivalent to two stereo channels; you can mic a drumset without overheads on 4 chanels)
* 37-note MIDI keyboard (critical for the kind of recording I do)
* Firewire interface (I'd rather stick to Firewire over USB, because I use Macs as well as PCs, and enjoy the compatability Firewire brings)
* Audio I/O has preamps built-in
So if I use it, I may have to retire my mixer board. I can also be fairly certain that the preamps aren't really professional-grade, but from the mixed reviews I've read, it suits the function of an on-the-go multiple-purpose interface pretty well. It has the XLR mic input with phantom power, is bus-powered (though I don't know how well that works in practice, since most laptops use the i-Link style Firewire interface, which doesn't provide power), and you have everything in one package. Hook up laptop, hook up one device, plug into that. I'll have to go play with one in a music store soon, though.
The thing is, there are a zillion choices. Where you go is up to you. Nobody's going to be a better judge of what you need than you
You have to use your ears. Go visit a music store. Hear some products in action. Figure out how many tracks you want to lay down at once, what software and operating system you prefer to use, and that kind of thing.
Anyway, I advise starting at the center and working your way outward. The heart of your DAW is your software package for multi-track recording. I use Cakewalk Sonar, and really like it. You might like a different one. Then get your decent-quality offboard DACs. Then you'll realize your existing microphone is crap, and find a good deal on a condenser mic for about $200 or so. Once you have a good mic and a good DAC, you'll start to be able to hear that your recording room isn't so great, and you'll sit down to figure out how to create a better depth and tone in the room you're miking.
So you start reading tips on miking stuff, and realize you can't do it all with a single large-diaphragm condenser mic. You realize you need a second one, and probably a stereo mic to boot.
$600 later, you realize that your existing DAC is only 2-channel. You need at least 4 for 2 mono mics and 1 stereo mic. Back to the music store you go, picking up something like the 4-port Firewire Audiophile.
Unfortunately, this forum isn't the best repository of knowledge on recording
Try harmony-central.com's forums. You have a bunch of guys there that really know their stuff, a massive list of FAQs on most every home studio recording question imaginable, and a lot of posts to cruise through to find answers to your questions.
Anyway, the recording setup I'm working out? A Dell Inspiron 9300. External hard drive. Ozonic, if possible, though I may have to settle for using my existing MIDI rig with an Audiophile. I already have several condenser mics and a mixer. Several stands, soundproof room, all is good. Get trackin'.