Diminishing returns, the biggest hold up with mechanical hdd's, is multitasking and the grinding to a halt of the system when you try to load more than one thing at the same time. SSD's main feature is that is just not there anymore, everythings nice and quick and basically instant to respond, programs open up instantly because seek times are gone more than the massively high speeds.
Games load faster, because the low end performance is SO much higher.
The problem is, theres a base amount of performance you need to get rid of all the irritations of a mechanical ssd, and 3 ssd's in raid 0 is so far beyond that, you really won't notice any difference.
I got 2 Crucial 64gb drives, I had two of the cheaper samsung 64gb drives from about a year earlier, both in raid. THe crucials were a decent upgrade as the samsungs obviously had the older controllers and did grind to a halt now and then, though it was rare.
The upgrade to the crucials was noticeable but nothing big. When one of them died I RMA'd it and ended up running them as single drives, I don't notice a single iota of difference between them in Raid 0 and single drives. Windows loads just as fast, games load just as fast, I still never get the system grinding to a halt, I just had less trouble installing windows and less issues if the install goes **** up at any point.
Basically I'm saying, get a single SSD, if you truly need more performance, try another but don't be surprised if you can't tell the difference in anything but a hard drive benchmark.