Not sure on DM's setup as my issue hasn't arrived (probably my recent move to blame), but have you looked into skipping all that and diving into drive caching with a z68 chipped board? You can use a 240G SSD (or whatever) and store everything else on spindles. It's slow at first, but it learns what you commonly do and gives those SSD speed even if it's on the spindle.
I just bring this up, not only because it's useful...but because 6TB's of SSD's takes a house mortgage to purchase. A 1TB OCZ Colossus LT is $2,864 at the time of this post, so 6TB would be just over $17,000 dollars...and it's still S/ata II. This can get really deep to make it work, but at some point we gotta get to the reality. $17K in drives for just 6TB would make Google even shudder, let alone anyone else. We haven't even gotten into actually RAID'ing them yet either, and this would need more than a software controller card...that could be another $2K in the least.
A dream machine is just that, so we gotta be careful about dreaming and reality. RAID the two Vertex's (vertices?) and see how much you notice the difference before going forward. This could get interesting though...