I run a 250HQI setup on my tank, yes it's very bright but it looks great and the sps and clams really love it!
The heat really wasn't an issue with just one fan, however the bigger concern is the evaporation. I lose anywhere b/w 1/2 and one gallon a day, which in a 29 gallon tank can really mess with the salinity. I use a doing pump and it dose a great job.
Definatly go with a MH if you even think you want to keep sps or clams.