{Q} HDD replacement

Would it be possible to remove my 2tb 3.5" HDD and replace it with 2 2.5" 1tb HDD. I'd like to fit one inside a HDD DVD Caddy like this; http://www.ebay.co.uk/itm/SATA-to-S...es_HardDriveEnclosures_RL&hash=item5d4ffefb59, and fix the other to the top and free space underneath the GFX card and hopefully help with heat displacement. I don't need the DVD drive so this seems like a good idea, to me anyway....

Any thoughts.