I just acquired an MRS-1266 for $750; the USB was $99 and the CDRW was $50 (you can use an off-the-shelf version instead of Zoom's).

It is a killer unit, so far; the drums sound great, and the interface is extremely easy and well thought out, whith the possible exception of the phrase looping, which may not be quite ready for prime time.

If you don't need the 6 channel input, the MRS-1044 (now discontinued but still sold) is available for a street price of well under $500 (It also includes the drum machine).

And CoolEditPro 2.0 will open the tracks directly from the internal 20gb HD via the USB port...