This card has been around here a couple of weeks only. I don't know if I'd rig a 24/7 machine on it yet. And who knows what will happen at the next OS update, and the next, and the one after that,...
What you ask can almost be completely taken care of by the Mac Pro without extra cards. You can rig 4 SSDs (and more) on the SATA2 controller and already have a significant performance to load your library, and it's not even sure SATA3 would best that. RAM is what you need most of all. Backup can go through firewire or eSATA.
And there is little advantage to using a SSD for you DAW project files - the only thing that is speed sensitive is the sample libraries. If you need a scratch disk for something else, an SSD will certainly be fast, but the constant write cycles will present a problem from a longevity standpoint. As most major creative apps have been going to 64 bit, the need for an uber-fast scratch disk has been decreasing assuming you have enough RAM.
I am doing the exact type of work you are asking about, and the only thing (other than a boot/app drive) that will remotely warrant the cost of SSD is the sample libraries.
The first step is to make sure you have at least 24-32 GB of RAM, then the only issue is whether you have enough large libraries to need to use SSD to reduce the Kontakt/Play pre-load buffering. Also be aware that trying to run EWQL Hollywood Strings or Hollywood Brass on a Mac is not advisable due to the EW PLAY app being a POS on OS X. Everyone who is serious uses a PC/Windows slave via Vienna Ensemble Pro to host those. Your Kontakt stuff (and probably EWQLSO) will be fine on the Mac.
Without providing more info on what all you use your Mac for and the specific libraries and size of your template, it's hard to make specific recommendations.