my experience with the RPM is that its not noisey at all and has ALOT of output. that said, i didn't care for its 'overdrive' sound. its distortion sounded artificial to me, which was a surprise, since my PSA-1's distortion is great, but other than that, i think that its a great sounding preamp.
i prefer the Ashly BP41 and the Yamaha PB-1 over it though. never had a Demeter VTPB 201, but do love my HPB-1J, which i think is in another league than all of those previously mentioned. IMO, Alembic's F2B and F1-X are also on par with the Demeter.