If it's too much then me wants 300 watts. I have 7ft. Height, 77" width, and well, a full 2ft of width if you dont count the edge of the closet opening on either side.
It's really not too much now that we see your dimensions. (13ft² give or take) 23W/ft² give or take.
I'm running about 275W in my 4'x2' (8ft²) right now, and I have plenty more power if I need it. (About 165W more)
Centre light only running at around 75W.
I'm able to keep it between 24-25°C with barely an effort, even when cranked up a little more.
It's definitely not too much, that Mars. It wouldn't be enough for me and the way I like to overpower things lol!
I might even do the QB96 option someone suggested with that space. Damn good lights.
You have plenty of great suggestions. Best of luck with whatever you decide.