no you dont need 4 250 watt lights, 1 1000 would cover the area with one light and it has alot better light intensity than the 250's.
you really didnt say how much you wish to yield but you can probably get by with 400-600 watts but you shouldnt need to use the whole 4 by 5 space if you go with a smaller light and just place it in a corner so you have some good reflection from atleast 2 walls and an air cooled reflector or cool tube is a good idea no matter what light you wish to use.
bejay Reviewed by bejay on . HELP! 250 HPS or 400 HPS??? I will be flowering 4 plants, maybe 8, in a 4'x8'x8.5' high space that is well ventilated...Want to know whether I should go with 2- 400 watt HPS or 4 250 Watt HPS? Rating: 5