I would try to steer as far away from software RAIDs as possible if you're looking for performance, especially for write performance. This might not apply as much when you're using software RAID 0, but it seems to me that it would make recovering your data that much harder if something goes wrong.
You may want to have two RAID sets anyways, one set up for performance and the other for capacity. You could shove all your non-performance-sensitive stuff in one huge RAID 5 and put your few performance-critical things into a RAID 10 array or something.
I would invest in a couple of battery-backup units for the RAID cache (little modules that cost about $120 each). That's what we do when performance and data integrity are both important. In that case, you might also want to disable the drive cache in the controller settings, but keep the controller cache enabled. You don't really need to worry too much about this if you have a UPS, but if ensuring every write is somewhere safe before telling the application that it is written are absolutely essential for your data integrity requirements, then you should do it (also, if this is that important, you need to do some tweaking on your virtual iron machine and the guest operating systems, too). But remember, you should always have a plan about what to do in case your RAID system completely fails (like, tape-backup or a physically isolated and time-delayed disk backup).
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