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?

well considering the space you could easily use 2 1000 watt lights but a bit big of an area for only 4 to 8 plants have you considered buying just one 1000 light and only using half the space in the room.

SORRY...The space is actually 4'x5'x8.5' high. That changes everything, huh?

a little but its still a good size for 1 1000 watt light maybe you should look into how much you want to yield at each harvest and it may help you decide what size light to use, for the space the 1000 is probably your best choice but its probably a little big if your just growing for your own personal use.

YES, just personal use...A 1000 watt with a cool tube be my best option?

...So, the 4-250 watt HPS lights are not the smart option?

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.

OK, I would like to harvest at least a 1/4 - 1/2 pound or more each harvest...Is this possible in the space I have? Let me also add that this space has a six inch AC vent coming into it as well as a 6 inch exhaust fan.

BTW- My wife and I like to cook with it so the more we can get the better.

you should be able to yield that much from a 400 watt light and just remember if growing from seed you will be looking at about 3 months maybe a little more from seed to harvest.
if you have a seperate space for mother plants and to start clones vegging you can reduce that time to around every 2 months for a harvest.
if you did decide to go with the 1000 and use the whole space you should have no trouble yielding over 1 lb with most strains and with some experience and high yielding strains some are pushing close to the 2 lbs per 1000 watt light with out using co2 just to give you a rough idea on yield if you went with the larger light.

WOW! In a 4'x5'x8.5' space? How many plants?

I guess I should add, I was planning on using an Ebb & Flow system that I built...It would hold 8 easy...It is 4-14 gal rubbermaids with a 25 gal res. I could easily go with 6- 14 galllon rubber maids/
.

Yes, I will veg in seperate area.

yes in a 4 by 5 space if using the 1000 but most will run alot more plants than 8, and just keep them smaller you might read up on sog wich you can use up to 4 plants per sq ft, and flower just rooted clones, you can get good results even if you dont use a sog method but you would still be looking at 15- 20 plants preferbly clones with a 3-4 weeks veg time. but you will generally always have better results if you can keep the plants shorter and the canopy more even both of the above styles generally results in plants 1.5ft-3 ft tall at harvest.