I'll see if I can help get the list of what you'll need started for ya'.
You'll need a good protein skimmer. For a tank that size, an AquaC Remora or Remora Pro would be perfect. You can get a used on Ebay or RC for $100-$150
Lighting - Your 45 shouldn't be all that deep, so you may be able to use T5's instead of spending more on Metal Halides. Your SPS options might be more limited with T5's but more and more people are claiming great success with T5 only tanks. Figure $500 - $1000 depending on what you get.
Water circulation - Closed loop or powerheads, figure $100 - $200 depending on what you do.
If you go with a sump and/or refugium, you'll need a good pump for it. Shell out another $50. If you go the build your own route, the acrylic you'll need isn't that expensive.
Heaters - you may be able to reuse depending on what you have.. if not, they're cheap.
Chiller - Whether you need one or not will depend greatly on your lighting. I personally dont have one on my 90G b/c I dont need it (Water stays at 81 24x7 this time of year). I know people with similar setups that needed a chiller though. (I extended my canopy by several inches to move the lights farther away. I also have several fans blowing across the water at strategic spots in the tank.)