UT2K3 and UT2K4, I believe, are both based off the same engine. Larger maps in 2K4.
I disagree about the noise level of the artic cooling silencers. I had one on a 6800GT, and was very disappointed by it, far louder than any of the other fans in my system. I also did not like the airflow it produced in my case. It seemed... counterproductive.
If you've already put down $1,000 on your video cards, and have a pre-existing water cooling loops, might as well lay down $100 for GPU blocks. This one is pretty good, though we don't have any empircal data for it (obligatory statement, this is Procooling after all) :
http://www.cooltechnica.com/Merchant...egory_Code=VCW