Apple drives or OEM

I have a stock Apple G5 XServer Dual 2 Gig processors and three 233 gig Hitachi Serial ATA drives. I have my OS on drive one, faculty homes on drive two and student homes on drive three. I need to increase drive capacity for students. Apple does not sell a larger drive as a retail part. I can buy a 400 gig drive as a service part #661-3360. Should I do this or can I buy a 500 gig Western Digital Caviar se16 model wd5000aaks. Take the old Apple 250 gig drive out of the Apple drive module and put the WD in it.