I'm looking to purchase a new HP ML370 G5, with the external MSA50 enclosure. I'm debating between the 72GB and 146GB 2.5" 10,000 RPM drives. The 72s provide adequate storage, but I'd like the know if the 146s have a higher sustained read speed. I thought they had twice as many platters, which would indicate they could sustain double the read speed. Are my assumptions way off? Thanks.