The reason a 960 EVO which is supposedly 6x faster than a SATA drive only shaves a few seconds off load times is because the 6x speed difference is at sequential read/writes. The bottleneck is 4k read/writes, which are still far below SATA 1 speeds, much less SATA 3. They're about 30-100 MB/s. (In fact, this is where most of the speedup of a SSD over HDDs come from. HDDs only get around 1 MB/s at 4k read/writes, so SSDs are 30-100x faster. HDD sequential speeds are around 150 MB/s, so SATA SSDs are only about 4x faster.)
Very little drive activities depend on sequential read writes. Copying large files (movies, backup archives) from one SSD to another, real-time video editing, and disk benchmarks; that's about it. So unless you're doing real-time video editing, or constantly shuffling a huge movie collection between SSDs, or running a benchmark to impress your friends, you're actually better off ignoring the sequential speeds and focusing on the 4k speeds and IOPS when selecting a SSD to buy.
RAID 0 doesn't help with 4k read/writes. Since the smallest sector size is 4k, all you're doing is taking a 4k or smaller file, splitting it in half but padding each half up to 4k (so now you have 8k of data to write), and each drive writes 4k of data. In fact once you add in the overhead of splitting and padding, software RAID 0 actually ends up being slower than a single SSD at 4k read/writes.