I envy you as I had to settle for the P7. The P9 is one of the most elegant looking turntables IMO.
The 2M Black is very very good I have no doubt. http://www.soundstage.com/vinyl/vinyl20080601.htm
But why aren't you considering MC? I see that your C2300 pre caters for MC too.
Personally I would stick with the original RB1000 endstub/counterweight solution and also keep the original white wool Rega Mat. And not use any type of clamp. This also makes it easier changing sides/records while spinning (not shutting off each time). The Rega way.
A 12" record is slightly larger than the Rega platter so it's easy to grap the edge of the LP.
I can recommend the white belts (they are not really white but more cream colored). The first batch (when they were limited edition) were more white but they were not as precisely and well-made as the current cream colored ones. Definitely get 2 of those.
Oh and I always give the platter a small push to get it spinning slowly before pushing the On button on the PSU - to minimize strain on the belts and motor on startup of the platter. But leave it spinning (as mentioned) until my music listening "session" is over.
Apart from the upgrade belts I also bought Regas own extra heavy counterweight (for heavy cartridges like my Ortofon MC Jubilee) plus Regas adjustable VTA spacer (gives you 2, 4, 6 or 8mm height increase without having to remove the tonearm completely from the plinth every time). For many cartridges you simply need to raise the armheight to get correct VTA.
I also listen to music with the dustcover completely removed (easy to do) as I feel that this sounds slightly better but that can be debated.
And you have to place your new P9 on a rigid lightweight wallshelf (bolted securely to a solid wall). Preferably Regas own RWB. Does wonders for tightening up the sound and especially the bass.