Aftermarket air like the Accelero don't sufficiently cool the VRMs so dont really enable more overclocking, though they are quieter.
The best method currently is to get a G10 AIO Water Cooler bracket, and the Gelid VRM Heatsink kit for 290 and install an AIO cooler ont he 290. It'll run extremely cool and quiet, and your VRM temps will be pretty good too provided you have enough case airflow.