2' x 4' x 6' grow tent lighting?

I have 2x4x6 grow tent and a six plant drip system that fits neatly inside it. What would be the best light and/or lights to put inside of it? I've been looking at some of the cool tube setups, and it seems that the 1000w light is only like $10 more than the 400w (both are cheaper than the 600w). Would this just be way to much light? And are the hps bulb upgrades that most places offer really good enough to veg with, or should I get a switchable system or even put both an mh and hps light in this little area?

would probably use either a 400 or 600 as the 1000 is overkill the 600 does have the advantage of better light penetration if you have good ventilation the down side to a 600 is you probably wont find a switchable ballast in 600 and the bulbs are going to be expensive as a standard hps bulb isnt available that I know of in 600 which explains the higher price.
you can veg using a hps while a mh or bulb upgrade is slightly better spectrum you will still have decent results even using a hps for veg you might want to pick up a light meter also so you can tell when the light output is reduced and you will need to change the bulb as maintence to maintain good plant growth.

im using a 1000 watt hps light in a 3.5ft x 3.5ft x 7ft, over 6 big bud plants. in an air cooled hood this works perfectly. my temps never rise above 79 F. i have a 265 cfm exhaust and a 180 cfm intake fan and i got no heat problems whatsover.

Hey Beanie
I have a 400Watt electronic ballast and it runs both MH & HPS blubs.
All I have to do is change the blub and plug it in.The ballast runs cool & no noise or heat.Some of the switchable ballast have a switch you have to flip when you change blubs.With an air cool hood & a good fan you wont have any heat problems.I checked a few sites for the 600w blubs and they have both HPS & MH,but they cost about the same as the 1000 watt blubs.I have a 400 Watt GALAXY electronic ballast & a 6" air cool ECONO Reflector with both HPS & MH blubs.There in a 2'wide by 8' long by 8' high closet that I put a air condition vent in the cealing to cool the closet to around 72* to 80* all the time.I veg with the MH & switch to HPS in the flowering stage.It works for me. Hope this puts some light on things for you.