the 90w will. WHat you do it remove the old psu then you insulate the underside on the DVD tray and mount the opus with blue tac or summink to the underside of the DVD tray. Its a ****in tight fit but ive done it and its not that hard. Just be carful not to knock any components off and ensure it dont short on anything. Thats why u insulate it. I knocked one component by accident and had to resolder it. Be especially carefuly with the ones nearest the little boards at the front, some on the opus can come close to touching them but when adjusted correctly they sit a good few mill from it. Also u will have a ATX power cable (big socket thing with loads of wires) ones with the opus and one with the case, use the one with the thinner wires, its easier to route round a capacitor on the front/right top corner of the board. The board can rest on the fan guard without fear of it hitting
This mounting method works will with a few cases it seems as i now have a diffrent one (Travala C136) and ive done the same.
Hope it helps