If you are looking to increase airflow, pick up a few of these 250CFM fans! Lol
Seriously, though, just boosting the fan speed, like smartalco said would work unless you're concerned about noise, because GPU fans are LOUD.
MSI K9A2 CF-F AM2+/AM2 AMD 790X ATX
AMD Athlon 64 X2 5000+ BE @ 3.0Ghz
Scythe Kama Cross 100mm CPU Cooler (Stupid thing BROKE, got a AC Freezer 64 Pro)
G.SKILL (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 @ 4-4-4-10
Nvidia GeForce 7900gs @ (And it's dying! ONOZ!)
Cooler Master Mystique w/ 2x 120mm fans
Antec TruePower Trio 430W PSU
Windows XP Pro x64-Bit/Ubuntu 8.04 64-Bit with Beryl
How to get easy lulz