Yeah, going SSD lowered the noise, and temperature of the MBP by quite a bit. The fan rarely if ever kicks in now. Handbrake also freaking sails through it's queues now.
It did require some slimming down my disk usage however. I found I had 4 office suites, 4 browsers, about 8 media players, etc... I picked the one or two of each and that thinned out the herd by quite a bit. Cutting down my iTunes library to about 8GB of video and music also helped. I now have a pretty sleek 40GB install (including an 8GB WinXP VM). It takes maybe 10 minutes or so to back up the whole thing, which is nice. With free space in the 60+GB range, I have plenty of room to add video, VMs or whatever for when I travel.
I also did what you are planning ie: a RAID served up over a Mac Mini feeding iTunes media to my AppleTV, and Time Machine space to everywhere. It's also where I store all my .dmg's, installers for Mac and Windows, and Linux distro .iso's. I can honestly say that I'm pretty happy with the whole system and for the first time in a while, and have no complaints with my setup.
I'm keeping the MBP for now as I'd like to see how Snow Leo runs on it. My wife is pretty attached to the Express34 slot as well. Let us know how it goes with your new ride. I think you will be pretty happy with the 15" MBP!
-Dave