I'm not running this plug-in anymore, but when I was it was in Cubase SX 2.0 primarily, and later in SX 3. The computer that I ran the plug-in on was a Hewlett Packard Pavilion dv 8000, consisting of a 3.0 Ghz processor and 2 GB of RAM. I ran everything through a MOTU 896HD audio interface. I can't ever recall having a problem with performance with the PSP Audioware PianoVerb. It's definitely designed to be a low processing power needing plug-in, as it's free and the idea is that it will be able to run on most, if not all systems. If you're having any questions, just try it for yourself.
I'd definitely encourage anyone with a compatible to go ahead and download the PSP Audioware PianoVerb. It's free and you won't find too many free things out there these days! The best part is that this plug-in actually sounds pretty cool! It's not groundbreaking by any stretch and isn't by far the best sounding software reverb out there, but considering it's free it's pretty nice. There's really no reason for you not to be downloading it and trying it for yourself right now...