Colt 6933, you'll never achieve hearing safe but you can achieve "manageable."
the only 45 cal option I can think of that would be practical for home defense would be a HK USC / UMP conversion and finding one that was done right will be hard and expensive.
There are a few 9mm options, but I'm not sure I'd want to bet the farm on a semi only 9mm. Someone with decent firearms experience can probably double tap the crap out of multiple home invaders and be fine, but if we are talking about somebody with basic firearms skills I'd say Colt 6933 or similar.
ETA: Saving $200 on a stamp should be your last criteria and integrally suppressed is usually more trouble than it's worth once you move past .22LR.
