C'mon guys, y'all sound like amateurs- let me help you out:
1. Yes, you do have to load the OS on the 2000. If you have a scsi drive attached to it, you can set it to autoload. (In fact, quicker than the flash rom option depending on what kind of drive you have attached.)
2. Don't waste your money on the Flash Rom. C'mon, how many times are you going to want the same sounds into memory every single time? Especially since you can buy a zip drive for like $35 off ebay and load the same program over and over... (At about the same loading time as the Flash rom...)
3. The 2000xl is the better machine because of the ability to hold 4 programs at once. If you can't figure out why, you probably don't need an MPC, a Boss drum machine should suffice. I don't recall the XL being able to hold more notes, but honestly, I never ran out of notes, and I use A LOT of tracks in my arrangements.
4. If you're trying to be a professional with your mpc, you should only buy: 32 mb of ram, a scsi drive, and the 8 output expansion card. Buy a cheap lexicon effect unit instead of messing with the Akai card. Also, if you're making beats completely from the MPC, you might want to invest in another filtering module, 'cause only having a lowpass will drive you insane after a while... Look around, there's better alternatives than the MCF 42, which is rather pricey, and is a digital filter....