more faces = more RAM
if it's a 1x1 pixel item, it'll have the same amount of faces as a cube and therefore use the same amount of RAM. this would also apply to any other square items (2x2, 3x3, 4x4, etc.)
due to engine limitations, i'm afraid exporting or importing files to or from any other program isn't possible. go use maya, blender, C4D, lightwave, or MAX if you wanna use .obj/.fbx files
when i pop top then your girl gave me just a little bit of lockjaw, babe he so cold he from the north he from the canada, bankroll so low, i ain't got nothing else i can't withdraw, ran out the door