Temperature Control Issues

Hi everyone! I have a problem. My grow space, a bathroom, is ~263cubic feet (minus around 12 for the vanity )
When I started getting everything together I went out and bought a Broan QTRE075C ceiling fan that moves a whopping 80CFM. I am planning to run one 400W Ceramic MH, and I'd like the option to add another down the line if I desire (I have a rectangular grow space, so less than optimal for a single bulb.) My only source of air intake will be around the bathroom door.
How much of a heat problem am I looking at? The bathroom is in my bedroom, but I won't be home for lights on/off so leaving the door open isn't really an option, plus I run into odour control issues. Someone at a local grow shop suggested I toss in an in-line fan, I believe (one that can handle 100's of CFM) but also said it would "whistle like dixie." The venting in the ceiling is 4".
If anyone has any suggestions it'd be greatly appreciated! Thanks and happy toking

I would look into air cooled reflectors for your (2) 400w HIDs. Hook the 4" inline fan up to the reflectors and you should be good to go.

My 6" inline fan is pretty loud. Maybe they could hook it up for you at the grow shop so you can hear how loud it is. There are ways to combat the noise too, like building a baffle box to go around the fan. You could always mount the fan in the attic if that's a possibility too.

that little fan wont help you much at all, with just one light. i would look at a vortex fan, they are very quiet. get the 6"(use reducers for your 4") and a speed controller, that will provide the flow you need and be very quiet.