Personally I don't think you can do better than a Sig P220. The only drawback is mag capacity IMO. There are a bunch of great .45's around. For 2 grand you can get into the top notch 1911's. But they're usually target pistols, not combat pistols. The P220 is a combat pistol. $2000 is a LOT of money for a pistol IMO. Generally people only spend that much when they want extreme accuracy. And extreme accuracy means tighter chambers which means less reliability.
That's why a P220 is a better SD gun IMO. It is plenty accurate out to at least 50 yards. But it is still dead reliable.
But these are general guidelines. I do know I saw a torture test of a P220 that was just incredible. It was posted online but it's gone now. Part of it is still available I guess. You can read about what they did
here on the Internet Archive but the photos won't be there. Still you'll get the idea. What they did to that pistol was incredible. It would have helped to see the size of the crane they used to run over the pistol and how far up they were in the helicopter when they dropped it. Plus the drop onto concrete from the top of that building was really impressive too. But shooting it with another pistol and it still working was the real proof of just how tough they are. The photo showed how much damage was done to the gun but it still fired. I'm telling you it was an incredible torture test and by far the hardest treatment I've ever seen any gun survive.
Anyway that's what you get when you buy a Sig. Plus Sig guaranteed the P210 to shoot a 2" group from 50 yards and that was before the P220 was designed and produced. The new P210's are guaranteed to shoot a 1" group at 50 yards. That's mighty impressive for a combat pistol IMO.
The P220 is a fairly big gun but people forget that the frame is aluminum. It's not as heavy as a full steel pistol. That certainly doesn't keep it from being tough though.
There are some other guns I think are great combat type handguns that are really good for SD. The HK USP is a great choice. And truth be told most of the 1911's are going to work very well too. I just don't think you need to spend $2000 to get a top notch defensive handgun. I think the Sig P220 is as tough and reliable as it gets and they are about half that $2000 price. I've had mine a good while so I didn't pay that much for it. I've got at least 15,000 rounds through it and it still runs great. I keep it in my desk drawer just in case. Of course I have guns all over the house but I sit at the desk a lot. I keep a bunch of mags though because like 1911's they just don't hold as many rounds as I would like. That's where the Springfields come in. I have a XDm .40 that holds 16 + 1. I know that's not a .45 but I bought it before the XDm .45 came out. Those hold 13 + 1 rounds which is great IMO. Heck I have a Taurus PT-145 that is much smaller than my Sig that holds 10 + 1. That thing is amazing how they squeezed so many rounds in such a small space. It's never had the slightest problem as far as firing but it is no Sig. Neither is the XDm. Sig makes a freaking nice pistol IMO.
BTW that $2000 could buy you a new P210 Legend which is a remake of the original P210. That is probably the best pistol ever made IMO. But it isn't a .45. It's a 9mm but it's been called
the perfect pistol by some. It can be bought for under $2000. That guy talks about getting 1" groups with any ammo. I don't know if that means the claims of 1" groups at 50 yards is bogus or it takes special ammo or the guy just can't shoot that well. I've shot 2" groups with my P220 plenty of times at 20 yards or more. Heck I've shot groups like that with my Taurus.