The 7850 will be a good upgrade to a 5770, they are worlds apart. Your current 750W PSU will be perfectly fine for that.
As far as LCD's go, a lot of it is personal preference. Everyone is going to throw their 2 cents in to what they think is best. Kind of like keyboards, mice, headphones. All of those output or input devices have a lot of room for argument. PC Components have benchmarks you can go by. Granted LCD's have performance reviews, but it is all subject to everyone's perception.