Storage Expansion required for HP DL380 G6 Server

Hi,

I am having a HP DL380G6 server configured with 8hdd's (4nosX500GB(Raid 5) and 4nos X 300GB(Raid 1 + Raid 5)).

As all the disk space is full and no more bays left to add new HDD. Kindly suggest me to the MSA storageworks for the DL380G6 server and the spares required for it ....

Opertaing system : windows 2003 server enterprise edition

RAM= 8GB

Thanks in advance..