...but I'd have to say that 4x4' or 4x5' could be lit by a 600w, going 1000w seems like wonderful, glorious overkill I assume that you're using the MH for vegging and the HPS once you flip it over to flowering... Use a rectangular reflector if you can... should light the space more evenly, though ymmv.

And can't remember exactly where I heard it, but something like 7,000 lumens/sq.ft is good, 10,000/sq.ft. optimal, and anything over 14,000/sq.ft. theoretically 'too much', but if bmwboy713 was pushing 18,000 and making it work, well, /wow/... I hope you were wearin' sunglasses while working on that killa show, mon!