With a tank that size I would go with T5's in addition to your PCs you are running now. MH on a 29 gallon tank will give you lots of heat and if you can control it with fans your evaporation will be pretty high - do you have a method of replacing evaporated water? You can probably run t5's off your old PC ballast as well with some new endcaps. Later on down the raod if you go bigger or decide you want predominatly SPS you can use the T5's for supplemental actinics.

-Erik