Instead of creating a RAID-0 array with the 2 drives, just use them as separate drives.
Use this software for your Steam games: http://www.traynier.com/software/steammover/
Yes, you lose TRIM when you have drives in a RAID array but it’s no big deal. Garbage Collection recovers drive performance.
There’s no fault tolerance with RAID-0. So if one of your drives dies then you lose all of your data.