24" vs 27" monitor

27" is the sweetspot, any higher and it can get uncomfortable in my opinion, don't worry about native resolution, most modern GPUs can run it that high with ease. Just note that you will need a much more powerful graphics card at 2560*1440.

I have a 27" monitor on a ~30" deep desk and it is perfect. As far as difficulty to run it is about the same to run 2560x1440 at 0xaa as 1920x1080 at 4xaa. I just keep aa off and my 7870 works great in all the games I play (mostly csgo and killing floor).

It says max resolution for your card is 2560 x 1600 (DL-DVI) your good, I would strongly go with 27" with no regrets.

If you avoid ultra settings and higher than 4xAA it should probably give you 30fps min, I put games on mix of ultra and high settings and get comfortably over 40fps minimum in stuff like Tomb Raider(I use TressFX in this one) with a 7970Ghz so if you do high and medium mix should work fine on a 670, you could probably squeeze in 2x maybe 4x AA on some titles.

Idk if it will still suffice when stuff like Star Citizen and the true next gen games come out though.

The PPI of your old monitor is 98.6. The PPI of the 27" would be 108.8 while the 24"ers would be 91.8 (1920x1080) and 94.3 (1920x1200). The higher resolution 24" will be closer to what you're used to as well as having the same 16:10 aspect ration.

A 27" at (2560x1440) requires scaling in Windows in order to make text readable. Not all programs heed Windows' calls to scale their dialogues and text, so some will be really small. That resolution will have pixels, any unscaled text, dialogues and icons that are about 91% of what they would be on the 20.1", that is, noticeably smaller than what you're used to.

In contrast, both resolutions of 24" will have bigger pixels, dialogues, icons, etc (104.5% and 107.4% respectively).

I had a similar decision last year (upgrading from a 20" @1600x1200) and I'm really glad that I didn't go for the 27". I was attracted to the greater pixel count but, while good for some graphics, hindsight shows that it would have made development much more challenging.

I'm not a gamer so I have no comment on that aspect. The greater pixel count may be good for games, if your graphics card and the game can cope with the higher pixel count but scaling of video 2560x1440 may even degrade the quality. I say "may" because I didn't get the 27" to try it out, so maybe someone can say from experience. I only bring it up as a possibility that needs to be checked out.

I think it might be handy if someone could do you a screenshot that matches your typical work environment, so you can see how the use of screen space is affected by the change in pixel size on 24" and 27". (In fact that might be a very useful article for Tom's to do for everyone's benefit)

As for which 24"ers to get. I got myself a pair of Dell 2412Ms, liked them, gave one to a friend and bought two more. However, as I say, I'm not a gamer, so I'm only recommending them for development, browsing, and watching the BBC iPlayer. A 24" in portrait mode is definitely recommended for browsing or having an Explorer in the one half and an editor or program window in the other.