Its all a matter of personal preference but Id much rather have a bigger screen. Thatll make for a much better overall gaming experience, be more engrossing and just all around better. 27" screens have taken a nose dive in price this last year.
[URL="http://www.ebuyer.com/390683-asus-ve278n-27-led-lcd-dvi-monitor-ve278n"]Here is an Asus 27" LED[/URL] for £208 that Id take in a second over a 24" IPS.
If at all possible, it wouldnt be a bad idea to get out and go look at some monitors actually set up and running. IPS does have the best color but TN is plenty fine for gaming and watching videos if you have a quality one. My HP is a TN panel and it looks great but my last Acer 22" didnt.
AMD FX-8150 @ 4.513 @ 1.39V
Asus Sabertooth 990FX
Corsair Carbide 500R
Corsair Vengeance low profile 2x4GB RAM
Western Digital Caviar Blue 320GB & 2x 1TB
EVGA GTX670 FTW @ 1070/1710
HP 2509B @ 1920x1080
BlackWidow Ultimate & Logitech G9