Those numbers (post #1) aren't strange for RAID0. It's RAID5/6 that won't be able to handle this much... (I've compared this, R0 can give >1000MB/s with 8 of the same drives as in post #1, but RAID5/6 with any number of drives won't pass ~700MB/s).
I ran this on the regular 1680, not ix.