Ssd and raid

No. You can RAID the two velociraptors, and the two SSDs, separately, but not the two together, unless you want to only use 64gb of each 500gb drive.

That being said, there are WAY better options for you.

Get a single, larger SSD - the larger the ssd, the faster it runs.

Don't get velociraptor - they're prone to failure.

If you get something like a 128GB SSD, and put your OS and most commonly used games on it, you can get a 1TB hard drive to store data on. That'll serve you way better than trying to use your SSD to cashe. It ends up storing mostly the same thing, but doesn't involve the PITA of setting up a cashe.