For big files, modern SSDs have already reached the data bus limit so you really aren't going to get faster than your motherboard. For small files, you are actually going to get worst performance because the RAID setup will add latency to every I/O operation and it won't read from both SSDs at the same time, since the file is below the stripe size (128KB or 256KB, depending on the controller and settings).

You'll actually get worst performance in most cases... Unless you are reading and writing large files