I run 2300w of Mars 2 LEDs in a 5x5 tent. The 700w is in the centre, with 4 x 400w units in each corner. This, in my opinion, is the optimum for coverage, although i would think replacing the 700w in the centre with another 400w would make little or no difference.
I wouldn't bother with the 1600w myself, there is too much of a risk that a driver will go, and then you're screwed. These lights are fantastic value for money compared to other LEDs, but there is no denying that there are issues with the drivers and power banks, which seem to be more common in the larger wattage units. If you have 4 x 400w rather than the one light, if a power bank goes you have backups in the tent, not to mention the better coverage.
Don't believe what Mars Hydro tell you about coverage. The 900w is about right for a 3x3, and the 1600w is good for a 4x4. If you really want the veg and bloom switch, and you have a 4x4 tent, then the 1600w may be for you, but if you have a 5x5 tent, you will lose yield from the edges of the tent if you go for the 1600w.
I've run these lights from seed (as in an entirely LED grow, no T5s or any other light has been involved at any stage) and so far they seem to be doing just fine. I'm currently at about day 45 of flower. Golf ball nugs rather than donkey dicks, but really frosty with shit loads of trichs.
The actual draw is just over 1kw from these 5 units.
I've never had any issues with temps, and can plug all 5 units straight into the wall socket with no problems.
Remember that vertical space is vital with these units, so aim to have anything up to 26 inches of space between the lights and the canopy throughout the grow. I would advise LST and a scrog.
I've also run the Gas Lantern Routine with these lights in veg and it works fine (12/5.5/1/5.5)
Ignore people who try to claim they don't like LEDs, or they think they aren't as good as other lights. I've learned that these people are almost always narrow minded, or in a position where they simply can't afford LED technology, so come up with all sorts of reasons to discredit them.
Mars II LEDs work and have all the advantages that LED lights offer a grower, if you can't afford them, stick to HPS, simple.