I've got a 2TB WD Caviar Green and a 2TB Samsung HD204UI in mine. I'm certain that it can handle two programs recording and a third playing back without a hitch. I don't know that I've seen it recording four and playing back a fifth at the same time.
The 7200-rpm drives are noisier and hotter than the 5400/5900 rpm "green" drives. I put a 3TB Seagate Barracuda
in my gaming PC a couple of months ago for $140.
i7-2600K, H70, P8P67-M Pro, 16 GiB, HD7950, SSD, 3 HD, Blu-ray, X-Fi Ti Pro, Antec P182, S75CF, 3007WFP+2001FP, RK-9000BR, MX518
i5-3570K, GeminII-S524, P8Z77-M Pro, 16 GiB, HD7770, SSD, 2 HD, Blu-ray, InifiniTV4, NSK2480, 55" TV; Asus UX32VD