Lighting help needed please :)

Hi there,was hoping for some help from some of you experienced growers please.
Ive got a 120cm x 240cm tent in which iv done 1 grow with 8 plants using 1 600w light.im using 1 5ft nft tank.
Now i know that 1 light is not enough for that area so i basically made a mylar partion to make the growing area smaller for the 1 light.
Im now thinking of buying a new nft tank to utilise more of the tent and put maybe 16 plants in,obviously i know im gonna need 2 lights but dont want 2 600w because iv used these in the past and there was so much heat.
So im thinking is there gonna be any advantage using 2 x 400w lights and more plants or should i just try and get a couple more in the smaller area with 1 x 600w light?
iv never trimmed the lower portions of the plant and end up throwing all the small crap stuff underneath away so maybe if i start trimming id still get the same amount and quality of good stuff on top with just the 2 x 400w?
Im gonna be using 2 adjustawing reflectors which iv found are very good reflectors for me.i know i could use more extraction but i dont want anymore noise for obvious reasons.
I spose i just need to know the best configuration for that size tent.
Thanks in advance
Idro

i have used two 600w in a 5x5 tent but had to open it during the light on period with an osc fan in front. are you willing to open and close every day?

I could without opening really mate?

if you've got the money invest in two air cooled hoods, a separate exhaust fan for it and another 600w light.
600watt bulbs put out about 90,000 lumens, some claim almost 100,000. 2 400watt bulbs are around 100,000...
it's a waste of money in my opinion. Wait untill you can afford to do it properly, mate

also, 600w lights are intended for a 1.2m x 1.2m area, so two would be bang on