The heat output of a metal halide isn't really any more than a fluorescent (when compared watt for watt), however they seem hotter because you have a concentrated light and heat source, rather than the heat being spread out along the whole bulb. THis does not affect the amount of heat going into the tank at all. For example, 1 400-watt MH will not heat the water any more than 4 VHO fluorescents, and you are getting the same amount of light. Considering the amount of light you can pack into a small place, I would have no doubt going with the setup you described before, if you are at all worried about heat maybe you could step down to 250-watt halides.
To cool the tank, just get some fans, and have them blow across the water's surface, you can even put one over the sump. When you buy your IceCap ballasts you can buy some cooling fans from them as well. A couple fans will increase your evaporation (which is good if you are dosing kalkwasser for calcium, if you've got a calcium reactor then it doesn't matter), and keep your temperature at an acceptable level. But really, as far as amount and quality of light, if you want to keep "everything" you cannot go past MH.