That's a lot of power for a 2 x 4 grow area. You don't have a lot of Width to work with.
Just my opinion, but I would use a 6 bulb T-5 setup and do a SCROG. That will allow you to maximize your grow space.
If you want to go with the bigger bulbs, I don't know if I would try and cram 2 400s in there. Maybe a single 400. And 600 would be overkill for that small of a space.
It all depends on how you want to grow. Fewer, bigger plants? Lots of small spikes in a SOG? SCROG? Do you know what you're plan is yet?