What is your current Giga machine?
I would recommend at least a P4 2.0Ghz or above processor with 1 GB of memory. Then you can do your compositions in real time without bouncing.
I have tested GPO in Kontakt on my PIII 733 MHz machine and was getting 64 stereo voices without problems. DFD is not needed for this library which allows for more voices. I\'m getting up to 200 stereo voices on my P4 2.4 GHz machine. Hard drive space needed is under what GOS uses.
Hope this helps.