the pci bus maximum transfer rate is 132mb but dont take it too seriously. its not like sata1 drives actually achieve a 150mb transfer rate its much less , anyway if your gonna get an sata pci card i recommend sticking to "promise" as far as i know their the best manufacturer in that field , but think about it from the capacity point of view if you wont buy an sata card then youll be able to buy a bigger capacity hd , as for replacing i wouldnt just take out the current and replace with the newer as its not data protection wise your better of having both connected for backup purposes just use some automated backup software, sure you can backup to other partition on the same hd but if the hd dies.. and the chances that both hds will die on same time is about 1 to a million , oh and btw seagate hds have 5yr warranty
