When you say "well-trained", define.
Military SOF? Basic military? Paramilitary? LEO? Criminal gang?
Are they coming into your house or the immediate vicinity? At work? On the street? Elsewhere?
To capture you or kill you?
Do you have ANY warning, or are you getting ambushed?
These factors all interact with each other to determine if you'll survive the encounter.
If they're military and it's their mission is to kill you, then you're dead, because you'll be cut down in an ambush with FA fire and frag weapons, or maybe a car-bomb, or a bullet to the head from a sniper a half-mile down the road, depending on how the officer in charge of the mission wants it to go down and what country you're in.
If this was Iraq, it'd be a laser-guided Hellfire through your bedroom window.
Paramilitary is much the same, though they're more likely to make a mistake that'll give away their presence and maybe give you maybe a couple of seconds to do something, though the lead and frags are still likely to get you.
If it's LEO's coming to arrest you, or criminals out to kidnap you, then you might have a little more leeway, as they generally try to take you alive, though either one will kill you if they feel threatened.
Criminal gang out to get you? Call the cops, that's their job, so let them do it.
The Miami FBI shootout and the Hollywood Bank Robbers were exceptions in many ways.
Platt and Matix were former military, well trained in the counter-ambush tactic of assaulting into the ambush, and had the mindset of escape or die trying, or maybe they just didn't give a f*** anymore and wanted to take out as many pigs as possible before going out in a 'blaze of glory'.
The Hollywood bankrobbers were just plain nuts. One had a brain tumor, the other amped up on 'roids, and both using barbital at the time as chemical courage.
They didn't really have much of an escape plan, or any plan for that matter, in mind when they went out for the last time. But they were armed for bear and wrapped up in kevlar with a plan to shoot every living thing they could if anyone got in their way, and that's exactly what they did.
Two men with rifles and a willingness to kill and no fear of death are more than most police are able to handle by themselves in the short term. Sure, they can call for SWAT, but that takes time to arrive, by which time people are bleeding and dying.
Anyways, these aren't the kind of people who'd you have to worry about, as they're after the money, and unless you work as an armored car courier/bank guard/cop, you'll likely never see these guys.
If you're worried about these kind of people showing up at your house, MOVE!
If you're caught in the cross-fire between these nuts and the cops, duck and cover as best you can and wait for them to sort each other out before you E&E out of Dodge.
The only other thing I can suggest is having overwhelming firepower yourself. How crazy you want to get with it is up to you. Grenades, flamethrower, toxic gas, claymores? Are you going to the local Stop&Rob for coffee or doing a tour in a free-fire zone?
If you're in suburbia, you'd be the criminal for having any of these things, as it rightly should be, 'cause you're obviously a nutter if you think anyone cares about killing you so badly that you need to be carrying this kind of hardware.
If you're freelancing in Iraq, then it's a war-zone and you do whatever you want as long as you don't get mistaken as a terr by a local Apache overflight, in which case things may get very...hot...for you.