you could use a pair of 250 watt halides if you wanted. i like t5s better because they put off a little less heat and you can tweak and adjust the color to your liking. using halides doesn't necessarily mean you will need a chiller.
no, you won't need powerful lighting unless you have photosynthetic creatures in the tank. live rock can do fine with just regular aquarium lighting.
Tek, fixtures from sunlight supply, or current nova extreme pro would be middle of the road fixtures that will do a good job for you. i would use a mixture of ATI lamps also. the better bulbs make a big difference.
there is no limit to what you can spend. you can even go LED
, but you have to be very careful what fixture you purchase. many are choosing fixtures according to price and are getting screwed on fixtures that can't support corals.
i used a pair of hydroponics fixtures over my last 24" wide tank. the 2 differences between hydroponics and aquarium fixtures are width, and price.
the hydroponics fixtures have much larger reflectors.
i used 2 of these-
Hydrofarm 8 Lamp 6500K 4' T5 Fluorescent Grow Light - Plantlighting Hydroponics
and then bought high end bulbs for them. you would only need one.
these fixtures have 2 switches so you can turn on just the 4 inside lamps, or turn on all 8 if you prefer. they only have one cord however, so you cannot put timers on the 2 sets of lamps unless you do some rewiring. the morning evening transition is not necessary anyway. that's just for human enjoyment. corals only absorb PAR(photosynthetically active radiation).
do you have a canopy for this tank, or will the fixture be hanging from the ceiling? i would keep the fixture about 6" off of the water if i could. mainly so it doesn't get splashed, and also so you can get your hand/arm in the tank with ease.