With a 40g, Id go with 2x150w metal halide lighting. With a 65, 2x250w MH would be better. But I have 2x150w on my 65g and its plenty of light, just have to keep stuff in the top half. I would think that retrofit with good reflectors would be better than a fixture, but I use a 36" sunpod and really like it. 14k Phoenix bulbs I use now, but you could use 20k radiums also.
But the key for sps is great water quality, which IMO means having a sump and refugium with a quality skimmer. I use a 20g with live sand and cheato and use a EuroReef RS100 as my skimmer.
Also need lots of flow. I use 2 modded mj1200s and a modded tunze 6025. If you have the money go with 2 tunze streams with the multicontroller.