Is a 400w really that much cooler than a 600w?

Ok, so I'm a stupid newbie who made the mistake of buying a 600w lamp for far too small of a space (120x75x75cm). I'm using a cooltube which generally does a great job of extracting heat. My tent has an average temp of 26C lights on.
The trouble is the temps close to the tube (4-5 inches away) where at the moment they are 32-35C and surely only getting worse once the summer kicks in and when the plants get taller.
So my question is, is it worth downgrading to a 400w? Do they run considerable cooler? I'd appreciate it if anybody had the temp readings about an inch or two under their 400w cooltube.

on a 600 you would never really want it 5 inches away, unless your just doing one plant. aim for a foot away from canopy. You could probably still use your light, but downgrading may be inevitable, I dont know what your temps are going to change to in summer.

Simply put. Yes.

I made the same mistake and it cost me, as I had to get a 400w ballast anyway, even a 400w kicks out alot of heat, but seriously, nowhere near the energy put out by a 600 (which is more than 50% more powerful in output in real terms in both heat and light, correct me if I'm wrong anyone).

The narrow walls, rather than lack of height are the problem, heat bouncing back as well as light and reducing falloff. I am considering fitting a sheet of glass hung just below my reflector to try and contain the heat better still.