Live or studio use? What kind of music do you play? The SVP-Pro is too noisy for studio use, IMO. There are lots of posts about its hiss factor if you care to do a search here. The RBI is much better suited for studio use.
It will be a totally live rig. I'm in a (hardcore) rock band. I do like clean tones sometimes, but I like a little grit to the sound as well. The RBI is working out fine, but I am interested in the SVP.
You need to see the old thread I started on this very subject. http://www.talkbass.com/forum/showthread.php?s=&threadid=71727&highlight=Battle+of+the+preamp
my svp just sounds so fat for me. the rbi didn't do too much for me when my svp was in the shop, though
i have the bass driver, and i also had an svp pro. i a/b'ed them because i was thinking about selling the svp for an rbi. i came to the conclusion that when playing by myself, i liked the bddi better, but with either of my bands, i liked the ampeg better. the ampeg seems to fit alittle better in a mix than the sansamp. (i play in two loud rock bands). anyway...i sold the svp, but for a mesa 400+!