There are several ways that you could increase the storage on your system. One would be to increase the size of each of your physical disks and keep your existing setup. Another would be to add SATA cards with eSATA external plugs and add additional drives to an external eSATA enclosure. My concern with external enclosures, however, is heat dissipation. Heat is often a destroyer of drives, but there are external enclosures available that address that problem. You could replace the case where you could add additional drives, but eventually you would be back in the same situation that you are in now. However, a combination of these options would not only allow you to currently increase the size of your storage but also allow for you to have room to grow in the future. That would not be the most cost-effective approach for short term growth but would be most effective for long term growth. Replace the case with a case that has more expansion bays for HDDs, add eSATA cards, upgrade some of your drives, and put the old drives in external eSATA enclosures. If you wanted to go to a rack system, then you would have substantially more room for growth, a specatucular setup, but would not be near as cost-effective. As for your HTPC software, I currently use XBMC in a HTPC case using an old PC with a core2 duo CPU and several gigs of RAM booting from a 4GB usb drive. XBMC covers everything that I need and streams my movies(h.264)/music(mp3)/pictures without an issue. I even bought some fancy remote to work with it, although my family prefer a wireless mouse over the air-mouse. My server uses an Antec 180 case with a AMS SATA Backplane Module modded to fit into the 5.25" bays. I still have room for a Blue Ray burner and I can fit 11 drives in the case, for a current total of 31 GB inside of one case. I use five 120mm and one 80mm SilenX fans in the case for quiet/reliability/performance. My two cents. Hope it helps.