Should I RAID My SSD?

no

you really won't see any improvement, and increase the risk of data loss. Use one SDD for the OS, and the other for apps and games

Get a 1TB Hard Drive.
The issue at hand isn't speed, its capacity. So adding another 128GB of fast storage isnt a good option compared to just adding in a large Hard Drive.

Also did you remember to move the pagefile? That's an easy [insert RAM capacity here] off the SSD.

No. I would not RAID your OS drive. I had the same issue and ended up with a Samsung 840 Pro 256GB drive. It was a lot of dough, but I am much happier than I was before.

I should probably add some more information.

I play Flight Simulator X, which currently uses about 55GB of space on my SSD, and is growing. I really don't want to move it to an HDD because the performance increase with having it on an SSD is huge. Therefore my two options would be 1) RAID my SSD with another identical one or 2) Move Flight Simulator to another SSD.

And yes, I've moved my page file to the HDD.  

Then that's what I'll do. Looks like I'm getting a new SSD for Christmas.  

Best answer selected by pckitty4427.