If you buy another rad, I think I'd just go with a GTX 360 or 480. GTX360
.With some decent medium cfm fans like these Pana...86cfm Pana
..These are the fans I use..115 Pana-S/W
.They will still do well with any 47+ cfm fan, but I would use at least those 86cfm Pana on any rad...120x38mm fans just have a lot more pressure and scavenge air through the rad better then 120x25mm fans will, even on lower fin per inch rads like the Swifty and PA......
...360 GTX Beats PA.3 Using 47cfm YL Fans
Good shrouds will knock off a few more C also...
..Part 1- Temp's with and with-out shrouds
..Poll: Push or pull configuration for Radiators
..How To: Make any Sized shroud in 2 minutes
..How To: Build A Performance Shroud
Since you already have one 320 Swifty you might want to just add another one like it..That would be cheaper and give you a lot of rad surface area...Its a little more restriction then using a single rad, but with your pump it wont kill you either...But really I'd just bite the bullet if you can at all and go with the GTX...Theres no rad that I know of that can beat it right now..Unless you want to use -47cfm ultra low cfm fans, then the PA is better, before I'd buy a PA I would just add another Swifty, they do well with ultra low cfm also, so it would be cheaper..