I am unsure, however, to get an ASUS TN 144Hz monitor and Nvidia 3D vision (I love 3D btw, I demo it in trine 2 by going cross-eyed on the side-by-side mode) or get an ASUS IPS pro art (one of the budget ones) so I can enjoy accurate colours and wide viewing angles.
Any opinions and suggestions for monitors or equipment will be greatly appreciated!
If it were me, I'd never get a TN panel monitor and only go for IPS panel (or better) with 1920x1080 minimum (ideally higher).
£350 is about ~$600 and I found this Dell Ultrasharp U2413 monitor. It's 24" 1920x1200, 16:10, AH-IPS, LED backlit, covers 99% of AdobeRGB and 100% of sRGB and is factory calibrated. Has height, tilt, swivel, pivot adjustable stand, 6ms GTG response time, built-in USB 3.0 USB hub, etc. and is $600.
Really comes down to what you think is a more valuable feature. Do you value 3D and higher refresh rate over accurate color and wide viewing angles? I personally think that an IPS is the best way to go, I can't stand the color inaccuracy that TN panels suffer from. Though many IPS monitors do have lower response times than TN monitors I haven't been able to discern a noticeable difference in actual usage. I like to use IPS panels for nearly everything, but TN panels just aren't enjoyable for me to use except whilst in use of gaming. Though even then TN panels viewing angles and color accuracy still do tend to irritate me. I prefer things to look the best they can be, and IPS has more benefits to me than a TN panel.
Though my suggestion is extremely biased as I don't like TN panels, and it probably would be wise to get more opinions. If you value the Nvidia 3D vision over the IPS panel benefits than you may want to go for it, you said your current monitor is horrible, if so then even a TN pannel would look a lot better than your current monitor.
You have a nice budget to play around with there. TN monitors will give you a lower response time, yes, but it is only a few milliseconds in reality. Whereas, an IPS panel suffers from a higher response rate, but honestly with the response time of all your components within and out of your PC, I highly doubt you will see a huge difference.
If I was able to go back and choose a different monitor, other than this BenQ I am currently using. I would most likely choose an IPS panel for it's larger viewing angles and better colour accuracy. It just seems like a better deal for me, as I have no intention of using the 3D capabilities built into this monitor and the colours look muddy, even after fiddling around with all the settings. However, if 3D is a must for you, pick up the ASUS TN 144Hz monitor and Nvidia 3D vision. But if you can live without, pick up the IPS panel.
As for resolution preferences, I have never experienced anything higher than 1080p as I am perfectly happy with the quality 1080p gives me.
Get a BenQ XL2420TE. Input lag is a bit more. But not enough to notice. And has a good image. For a TN looks just as good as my VA panel. All the ports and adjustments you would ever need. And a nifty carrying handle and headset hook.
If you can find one the old XL2420TX is only 120 Hz. And I don't think the image is that good. But had the sending unit for 3D Vision built in the bezel.
I use Dell U2412M which is a more affordable 16:10 IPS, same pannel basically but only 2 usb and standard DVI/VGA/DP. There's non-led (lamp) IPS that have less backlight bleeding (it's not noticable on the LED) that are more expensive and have more connectivity.
I am very pleased with it price/feature, the picture quality on this is better than most IPSes in this range, and response time is impecable in gaming. It's also very power efficient.