Hi there,
For around that budget your three best monitor options are either a 23in 1080p 120Hz TN panel monitor (like
this one), a 60Hz 23in 1080p IPS panel monitor (like
this one) or a 60Hz 24in 1200p IPS panel monitor (like
this one).
The TN will be better for fast-paced gaming as the pixels in TN panels can change faster than IPS - so you will see less ghosting when there is a lot of motion and fast motion will feel smoother due to the 120Hz refresh rate. However, compared to an IPS panel then colour accuracy isn't as good and crucially the viewing angles are much worse - so when looking dead-on and you move your head a bit, the colours will shift a bit. Also at the extremes of the panel you may see some colour banding.
On the other hand the IPS panel monitors aren't quite as good for fast paced-gaming as mentioned above, though these Dells are generally considered fast enough for playing FPS games on (quite a few forum members have these monitors and play games like BF3 on them - which they find run very nicely), since their pixel responsiveness is better than standard, cheaper E-IPS panels due to a rather well implemented pixel overdrive response. Also, if you are playing slower-paced games (like strategy games such as the anno series) then the reduce responsiveness of an IPS panel isn't likely to be much of an issue - but the generally superior image quality of the IPS (compared to a TN) will make these models a better fit for this type of gaming.
Also the Dell U2412M has a larger resolution that the others at 1920x1200 (compared to 1920x1080 on a 1080p monitor) so you will generally be able to see more on-screen at one time, which can be very useful for strategy games.
Here are some in-depth reviews of these monitors:
http://www.prad.de/en/monitore/review/2011/review-dell-u2312hm.html
http://www.tftcentral.co.uk/reviews/dell_u2312hm.htm
http://www.pcmonitors.org/monitor-reviews/dell-u2412m
http://www.prad.de/en/monitore/review/2011/review-dell-u2412m.html
http://www.tftcentral.co.uk/reviews/dell_u2412m.htm
http://wecravegamestoo.com/forums/e...samsung-s23a700d-120hz-3d-monitor-review.html
I can't seem to find many in-depth reviews of the S23A700D, however
this monitor is basically a DVI version of the S23A750D, so here is a review of this monitor (for playing games in 2D @120Hz the performance should be about the same):
http://www.anandtech.com/show/5231/samsung-s23a750d-3d-lcd-display
