T5s would be less to run, true. But don't rule it out. I never understood the shimmer everyone talked about until I got mine. I'd think you'd get away with only one unit and a 175 watt would give you some flexibility in your tank.
You don't need to follow the watts per gallon, as it is just a guide and not really accurate when you start factoring T5s into the mix. Sincerely, a GOOD T5 is the next best to MHs, some say they are as good or better if the shimmer isn't important.
really the T5's would be better than the VHO's? wow. even if i can only find 24 watt T5's? would i need to have 4 of those then? i'd like to just be able to add 2 bulbs to the 2 florescents i have now.
i do have a 440watt MH sitting up in my attic but wow talk about overkill..