Which is pretty hard to find because of the height of the case (how thick it is) limits that selection of possible video card to an even smaller number limiting the choices to <200W and low profile video card, the best card in that pile would be the GT1030 or GT 730 but both needs 300w PSU. this is not a good choice of system (In that computer case as mentioned earlier.) to use as a gaming system.
Why not upgrade the PSU? you ask... well slim case (SFF) use a odd shaped PSU and there are no "400w" PSU for such SFF cases to speak of or if you find one somehow, it will not be worth it due to the limited pool of video cards usable in the case itself.