Image quality wont be compromised by having the large screen. Just some people think that at that physical size you should have a higher resolution, otherwise the pixels are "too big". But there shouldn't be any problems with quality.
A 3570k can get to around 4.2Ghz before needing additional voltage, so aim for that unless you want to get into the gritty side of overclocking. A 212 EVO will hold that frequency fairly well.
As for how much performance you will gain, it wont be that much really. The biggest difference will be in benchmarks.