The RAM is for loading sounds into for actual use at the time of programming. Having 128 means you will be able to load like 8 times as many sounds.
The 80 gig hard drive is for storing sounds, much like the CF card. However on a much grander scale. Now I am not too sure whether you are abe to negate the CF card and just load sounds direct into the Hard Drive (i suspect you can as it would be rather laborious to use the CF card as a parcel transporter of sorts if you wanted to hunk a load of files onto the hard drive) but having the CF card is handy. If you have a card reader on your PC and you dont have your MPC sitting next to the PC all the time then it is handy for quickly transferring files.
I dont have a card reader on my PC (and I only have USB 1) so it's very annoying having to take the MPC into the PC room. Plug power lead in, plug USB lead in and then transfer files. Would much prefer to have a CF card reader and USB 2. If you have your PC next to your MPC anyway then I guess this isnt a problem.
I plan on getting the memory and also the hard drive due to the fact it gives you more versatility in storing sounds. However I am also hesitant, as this may be at the expense of creativity, as many people will tell you innovation and creativity comes from limitations and experimentation to express ones self within those limitations. The initial reason I got an MPC was because on the PC there was always more stuff/sounds to download/read/ try out which made it too easy to get distracted. Working strictly on an MPC for the time being limits me to working it and trying to express myself within tighter parameters.
Anyway I hope I've helped.
SUSHI
"The monitor speaker is a dog you kicked & it would bark in beat with the track playing, but sometimes if it smelt sausages it would run around"