Getting back to the original question of this thread.
Even if you have a multichannel audio interface, recording 8 tracks at once is going
to be pretty CPU heavy, especially if you will play them back at once and overdub new tracks. So your computer better be up to the task.
Now, the least expensive decent multichannel(8 or more ch) interface,presently, is the Maudio 1010LT(8 inputs). Also, I suggest you get a PCI interface rather than firewire or USB. A used Echo Layla24 is also good, as are the new Echo Layla3G models.
Lastly, get some decent currently supported software like one of Cakewalk Home Studio or Sonar, or even Yamaha/Steinberg's Cubase.
I purchased a 2.8GHz processor PC for my home studio, so I think it's got the ability to process multiple channels simultaneously. I would just like to start expanding my potential and I think upgrading to this multi-channel audio interface would be a good step in the right direction. I appreciate the advice.