metal halide question

im looking to invest into a metal halide for my 30 gallon aquarium. i have never used halides before only t-5s, so im going to need some info. i would like to know what type of wattage i should get 150w-300w? and do i really require a chiller or is there a way to wrap around that? i also cant do any suspension hanging, so its either clip on or mounting bracking. any other info is greatly appreciated! i do plan on doing LPS and SPS. also another random question, which would be better a 30 gallon long or a 33 gallon flat back hex?

 

why would you get halides, for a small tank like that t5's work just as effectively and in my opinion work better than halides for a small tank. how many bulbs is the fixture? also when i added halides to my tank it only went up one degree. overall i think the best way to go is to just keep the t5's

 

i have a 250 on my 30 gallon..tanks never gets over 80..