the issue as far as hp has responded is that the hp hard drives are preloaded with firmware to interact directly with the hp controllers and servers. this has not been put on the drives to disuade you ...
Techreport has a nice review of chipset integrated SATA RAID controllers. The (not so) surprising results: The single drive vs. RAID 0 CPU performance hit in HDTach was negligible. Typically <1-5% ...