If I want to test a single drive I can use HDtune, HDtach, etcetera to test one drive at a time. Unfortunately these tools don't help for testing software RAID. As long as Disk Management in windows sees the drives as separate items HDtune and friends offer to test the device not the volume.
With hardware RAID things are simpler as you can set up a volume equal to the array for benchmarking purposes before repartitioning.
I really like IOzone. It's flexible, open source, multiplatform and works with files. It might look a little complicated, but it's more than likely worth your while to spend a few minutes figuring it all out.
Among other things it will let you test scalability with multiple stream measurements, help you find the ideal chunk size, aswell as let you test with special options such as synchronous or direct I/O.
One option you might want to look at is Iometer