I would just put a 120 MM fan there such as a Higher CFM panaflow or one of Antec's. I have 3 hard drives (36 gb raptor, 200 WD, 400 Seagate) and all appears fine...
As you know..the Sonata is well...tight when you have a lot in there. Hence I'm moving to its big brother the P180 for my next system

. Much better laid out imo.