Seeing as how I can game with most of the goodies maxed out at 1920x1080 on an HD4890 and a Phenom II, I would say that you are incorrect about dual GPUs maintaining relevance at this resolution. Two things need to happen for dual GPUs to make any sense for the mid-range PC gamer:
1. The price of higher resolution monitors needs to come down dramatically
2. Today's graphics are highly dependent on consoles. Until the next generation comes out next year or the year after, we are not going to see giant leaps in gaming requirements.
I am also curious as to which closed loop coolers you have personally used that you consider "noisy," "problematic", and "leaky." I've used Corsair closed loop coolers for client builds without issues, noise or otherwise. This new Thermaltake line (made by Asetek) is supposedly excellent.
Are you maxing out Crysis 2, Skyrim, and Battlefield 3 at 60 fps with that hd 4890?
Just as prices dramatically decreased with the 1920x1080p monitors, so will the 2560x1440. Not only that, but there may be a chance the OP will want to run a triple monitor setup.
And as far as the closed loop coolers, there are plenty of reviews on newegg, amazon and other places. Here's a youtube video on it...http://www.youtube.com/watch?v=ouXXI_TS7KQ