I suggest you do a search on these boards. Watts certainly do matter. You can not put a night-light over your tank even if it gives off the correct spectrum. although it contribites to the intensity, wattage is not necessiarly THE intensity of the lights and I think it is probably the biggest misunderstanding. 150 watts of MH is much more useful to photosynthic animals (that require high amounts of lighting) than 150 watts of florescent.
Anemones require high amounts of lighting (believe me I have learned the hard way). I would reconsider purchasing an anemone unless you want to also get into small polyp stoney corals and/or tridacnid clams (which also need high intensity lighting), but to purchase an expensive light setup for one animal does not make sense to me.
As far as spectrum - 6700 degrees will produce the best results, but is not very pleasing to the eye (It produces a somewhat yellow light). You can run 6700 and suppliment with atinics, which looks great, or you can run 10000, 12000 or 14000, which are not quite as effective, but are much nicer to look at. I personally run 10000 with atinics and I like the colors that are produced.