is there any significant difference between IBM's 60gxp and 75gxp models? specifically, on their website it has that 60gxp models have 40mb/s sustained transfer rate, and 75gxp models have 37mb/s. this difference is probably due to 60gxp's higher density etc etc blah blah, but isn't the 60gxp LOWER model? thus meaning 75gxp should OUTPERFORM 60gxp, yet their website claims otyherwise? what's up, does anyone know anything about this? just trying to reassure myself in buying a 20 gig 60gxp so i can finally set up that RAID....