Thanks, Gary. For a single SSD drive to get Read speeds of 500MB/s+ and 2 drives in RAID 0 speeds of 1000MB/s+ is getting towards the interface speed limit, bearing in mind that it is 600MB/s and that you have to factor in operational overheads. I note that your Write speeds aren't as high as mine were when I was running non-RAID, but it is chiefly the reading of data and the speed at which it can be read that governs the overall feeling of speed of the computer.
In order to be able to go faster than 1000MB/s, we would need to increase the number of drives so that more SATA channels are employed for the array. For example, 3 drives should yield a speed of ~1500MB/s and 4 ~2000MB/s (I wonder if anyone has tried or could verify that?) and that really would be a lightning fast system.