Here's the results, judge for yourself...
1st is the original 120 GB SSD, 2nd is 2 SSD's in a raid0
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I'm sorry, but I'm skeptical about the RAID result. This would be in a PCI card, I presume, and not two drives in two normal drive bays? Otherwise, I don't see how you are getting such a dramatic (more than 2x) performance increase - that should not be possible.
For the OP: A typical upgrade scenario from normal drive bays would be a PCI-E card. One popular choice has been the "Apricorn Velocity X2" or the "Duo" version (not X1, which is slower). The former holds a single drive, while the latter holds two. They are rather expensive, though, but they could, with fast SSD's, provide up to around 3-4x the speed of a single drive in a single normal drive sled.
I do NOT recommend running RAID 0 for SSDs on one of those cards. Twice the likelihood of everything crashing, and in these systems the modest additional improvement in speed (maybe 50% max) is not worth it. Indeed, it turned out to be a big headache for me and I switched to non-RAID drives with perfectly fine speeds. Beyond some level, it becomes harder to detect subjective improvements other than by using a utility anyway.
Beyond that, you would have to get into various AHCI solutions, but these can be a pain on cMP's since only certain specific Apple drive solutions tend to work.
I think for the OP, the simple way to start is to just put an SSD in a normal bay. If you are a little more ambitious, you can put two drives in the normal bays in RAID 0. I ran two of them that way for years and it was about twice as fast as a single disk since it's the bus that's the bottleneck (I got around 300 MB/s). I'd do that again, but use a good backup solution like Time Machine (which can be on a spinner). It's not too far from a card solution in speed and it's super easy and inexpensive.
At present, I have SSD's in normal drive bays for older system versions, and a single fast SSD on an Apricorn Duo, non-RAID. The latter gets around 450 MB/s, only a little behind my old RAID setup. I scavenged one of my old fast RAID'ed SSDs for a different computer, and can't really tell much difference after moving to a single drive vs. RAID. Indeed, the over-all system performance actually improved, since RAID was causing some ridiculous lag during certain operations.
Finally, a little trick: Once you move to an SSD, your goal should be to eventually remove all spinners except for Time Machine. Otherwise, the Mac will constantly try to wake up the spinners before doing many simple operations such as even accessing certain global menu options - even when you aren't intending to use those disks. That's super irritating once you are used to SSDs.
