I guess what you're really asking is what's the best skimmer under $450 that will fit in the sump of your 72 bowfront tank.
My advice would be to first select your sump and then determine how much room you have for a skimmer (including height), keeping in mind that many skimmers, including SROs, need to be elevated above the sump level to perform properly. I'd also recommend that you not just look for the best skimmer that fits the sump and that costs under $450. Because you may end up with a skimmer that would kill on a 180 tank but not perform adequately on a 72. IME, bigger is definitely not necessarily better when selecting a skimmer for a particular tank.
Good luck,
Mike