Hey Jason--you are probably long gone but yes you can do a dual-boot OS9 and OSX HD for the cube and many other 2k era macs. The best place to look for info on this, is the Mac Liberation Army page. Great vintage Mac forum. I know the Operator Headgap Store also will sell pre-configured HD's with 9.2.2 or Dual boot OS's.
I wanted to post because there are a limited quantity of refurbished internal CD-RW/DVD-ROM drives on ebay right now. As most Cube owners know, the rubber rollers dry up on these, and they eventually won't eject a disc. I ordered one this morning and if you have a Cube with a bad internal drive, I encourage you to check them out while they last: