Seeing as you are willing to mod your case you can buy a Lian Li mb tray (http://www.frozencpu.com/products/20428/cpa-276r/Lian-Li_Replacement_PC-6X_Motherboard_Tray_-_Red.html?tl=g43c241s905&id=q8wFNKFN) which you should be able to fit into the T3400 case. I am also going to be doing this mod soon.
This will allow you to fit an flipped Micro-atx board into the case (not sure about atx).