hey go with a 250w hps you wont be disappointed I started under a twin bulb four foot florescent until I notice that I had a talent for growing, and switched to hps. the resluts are amazing heat isnt too bad just use some small computer fans or a four inch fan and your good.
Not a good idea IMO. I have grown with both, and I would say get the 400 hps. I have a pretty small closet and my heat is fine. I do leave my closet door open at least partly though. If you have to leave the door closed at all times and can't vent in anyway, you could use CFL's, but I think it's def. worth it to find a way.
yeah you should go with the 400 hps, you will get more yeild and better buds. just get some good ventilation in there with a fan you should be just fine.