PureOverclock posted a 2x1GB DDR Memory Roundup: 2x1GB Corsair XMS 4400 Pro TwinX, 2x1GB Mushkin XP4000, 2x1GB OCZ PC4000 EB Platinum:

The question of whether 2GB of system memory is necessary will depend on what sort of games you play, though anyone who takes their gaming seriously will be shooting themselves in the foot by sticking with 1GB. The F.E.A.R test alone shows how a system that is more than capable of playing the game with silky smooth frame rates can be brought to its knees with only 1GB of system memory. Lower end system will not benefit as much, though, as these types of systems (6800GS or lower) could never hope to run fluidly with all eye candy turned on any way. 2GB is highly recommended to anyone with a 7800GT or higher to keep things perky!

Moving on to the kits tested, all of them performed very well when you consider their prices, and so picking a clear winner here is impossible, it will all depend on your own personal needs. The Mushkin is a bargain at £170, with it's only downside being a lack of competitive timings at low to medium FSB speeds. If you are planning to run your memory at a high FSB you could do a lot worse than the 2x1GB Mushkin XP4000.

OCZ's PC4000 EB will attract many users due to it's low timings of 2.0-3-2-7 at 200 to 220MHz. THis is as good as it gets for 2Gb kits. Tight timings were managed all the way up until reaching its limit of 262MHz at 3.0-3-2-7. This may not be as high as the Corsair on test but these are some of the highest results i've seen for an Infineon CE6 based product. Add on the fact that these are £30 cheaper than the Corsair and you cannot ignore the fact that these are some tasty modules!

Corsair steals the show here with a no compromise product for those with deep pockets. At £244 they are the most expensive 2GB set on test, but they also offer the highest performance in every single test performed. If your looking for the absolute best and are prepared to pay a premium for them, the Corsair XMS 4400 Pro TwinX are the ones to grab.