Perhaps. However, my non listed drives, respond normal as far as read and writes over Samba. Several people have confirmed the same drives work great, source Newegg. I know the HCL doesn't list them, but that doesn't mean their not supported.
When the system was fresh with no created shares or storage it worked great. Now with it almost more than half way filled up the preformance has gone down. I wonder if more RAM could be an answer or perhaps the ammount of shares has something to do with it.