If you are running OSX Panther I recommend you purchase iLife and get the Garage Band software for $49.
Garage band allows you to record via the USB port. I think I read that it has amp emulation but I urge you to check online to confirm that before you make your move.
I intend to buy myself Garage Band, as soon as I upgrade my iMac and get an extra hard drive to Run OSX exclusively. (I run ProTool free version for OS9 only and intend to keep thing separated, running both systems independently.
A friend of mine says he got ProTool LE for OSX and it comes with a M Box interface (preamp). It cost him $500 but he says it's awesome and ProTools LE comes with more plug ins than you can shake a Les Paul
I hope this helps. [img]images/smilies/icon_thumb.gif[/img]