Thanks for the reply. I bought 2x SEAGATE ST31000524AS 1TB drives, given that I am not really running the RAID setup in demanding conditions (it's a soho server running for about 2-3 hours a day at most) and that, with their low price, even if they proved to be incompatible with the controller, I could use them somewhere else without having spent too much money on them.
Fortunately, they worked fine: they were accepted by the controller and worked (file copies from and to) for about 10 hours straight without being rejected. I'll buy 4x more one of these days.
G