You can certainly light a 2x4 well with that kind of budget. What I would suggest is going after one or the other first. In my opinion, 6’ height is going to limit you to shorter plants or scrog type grow if you with cobs. On the flip side, 300-400 watts of cobs will probably eliminate your need for any side lighting too. The problem with that is it takes some distance to not fry your plants. So in order to not have problems with that, I’m thinking your best bet would be to do something with the strips for the overhead light, and then run a grow or two with it before adding any side lights. You’re certainly in the budget to do a couple of quantum boards too if you’re interested in them.
Does that sound reasonable?