spiderfarmer sf2000 200w or se4500 and g4500 480w will fit in a 2x4
i run a sf2000 in my 2x3 but i think the panel is a bit small for a 2x4 so i would prefer the se4500 or g4500 even if you may not use them 100% close to the plant, they offer a more even light coverage on tent border than the sf2000