Hi,
I have done quite a bit of work with SSD myself. SSD have a good use cases depending on the workload. Read VS Write and Random VS Sequential. You also need to look at the long term PE of the drives.
What workload are you building this for? Database?
There are technologies in the market that let you have the best of both worlds.
Take a peek at this.. WWW.SanDisk.com/FlashSoft-Connect Flashsoft turns SSD into Cache so Random Read and Random write workload is handled by the SSD and Sequential Read and Sequential Write are bypassed and handled better by traditional spinning disk.
Note: You won’t need as much SSD in your design and the SSD won’t have to be RAID protected if just used as READ Cache.
Regards