Your setup would definitely be on the cutting edge, I know people are using SSD but I haven't heard of anyone going as far as you're proposing. I would probably upgrade things in stages, at least as far as the drives go, in order to see what works before committing to tons of it.
I don't know if raid is really necessary for SSD drives, it will give you more speed but the question is whether single SSD drives would be fast enough for what you need (and whether you'll end up saturating one of the other busses and not be able to use that much speed - unfortunately even the new mac pros only have SATA 2 and not 3). Personally I'm inclined to just split different sections/libraries over multiple drives instead of raid - as long as you split up the sections wisely, you're going to be splitting the load over multiple drives anyway. Also, if you get a raid 3 PCI card, you may want to use that for SSD and put hard drives on the internal busses - even a single fast SSD can saturate SATA2 but a fast raid may not. Personally I'm skeptical how much benefit a raptor provides, especially since most sample streaming tends to be more about seeking to many different places than transferring giant continuous chunks of data - seems like an expensive stopgap waiting for SSD to get more mature.
Instead of raid ssd for boot drive, I would get a smaller SSD for boot (assuming it will make that much difference, I'd probably make that the last thing I'd switch to SSD on a sample playback system) and put samples on their own SSD (or SSD raid). My guess would be that having samples on the boot drive is less of an issue with SSD than with moving platters and heads, but it still seems like it would be nice to keep them separate, especially with potential fragmentation issues or SSD specific quirks. Unless you are doing zillions of audio tracks, I probably would keep my sessions and audio tracking on a conventional drive, and maybe just a 7200. You might even want to consider USB for your time machine disk to keep it off the FW bus - the initial backup will take a while but once that's done the following backups are much smaller and faster. I usually run TM to a networked drive on another machine and even that is fine.
You definitely will want to spend some time figuring out which libraries (or sections) you use the most or put the most demand on the system to be strategic about what goes on the SSD and what goes on conventional drives. Sounds like you're doing that already. If you have stuff that isn't used that often, particularly if much of it isn't heavy on the computer or you only use a track or two of various things at a time, I'd try starting with it on 7200 drives and not worry about raid unless that's not fast enough. I'm looking at SSD soon and I'm going with a smaller drive and fitting what I need by using 16 bit samples with libraries that have the option, fewer mic positions, and the sections that are the most taxing with the others on standard hard drives. I'd definitely buy third party SSD instead of buying from Apple, it's just so much cheaper and way more choices. The SSDs apple use are just standard hardware, if they finally add a TRIM solution, it will have to be in software to support all the machines they've already shipped.
As for memory, I don't know what libraries you have specifically, but 32 gigs is a giant amount of ram and you may not end up needing that much (especially if you have a fair amount on SSD and can reduce the buffer). I would start with 12 or 16 (3x4 or 4x4) and see how that works and then add more if you need it. Even with a 64 bit app and plugs, it may be hard for a system to use that much, and that's an extremely long load time.
The 12 core machine looks amazing but unfortunately Logic isn't even fully optimized for 8 cores yet so I'm doubtful that it would be used to its full potential, at least with the current version of the app. Maybe VE Pro would help work around that, I don't know. Hopefully apple will update Logic soon, but nobody knows - if they do update, the 8 and 12 core machines will absolutely scream (especially with hyperthreading support, which already works on the quad machines). But if they don't, there's the possibility of cores just sitting there doing nothing, which is a bummer for a machine this price.
Overall, I'd get the base machine, one SSD and a couple big internal drives to start. Start loading up libraries, create test sessions, and see where you need more capacity or speed (or not). Even without full optimization for Logic, even the 8 core is a vast improvement over a quad G5. I don't have much Vienna stuff, but on an 8 core MP with 12 gigs of ram and samples on a couple internal 7200 drives I'm able to load up a full orchestral template of EW platinum, keyswitches on every instrument, plus LASS and some other things. I can get tons of polyphony if I need it and for most full orchestral things the CPU use is surprisingly low. Obviously the big vienna libraries and things like HS are way more taxing, but I feel like this machine could handle a fair amount more with SSD. Assuming Logic gets updated at some point, that's another major boost.
Hopefully all this rambling will be helpful in some way. Let us know what you end up doing, I'm sure many users are looking at similar decisions.