|Depending on the motherboard, you may be able to overclock your processor to around 3.4-3.8GHz. |
"Would upgrading the CPU make a noticable difference while gaming?"
Not enough of a difference to warrant the upgrade. If you can, overclock your current processor, or wait until the AMD Bulldozer and Intel Ivy Bridge processors are released and build a new system.
Socket 939 | Dual-core Opteron 185 @ 3.2GHz | 4GB | 1.0TB | Win7 x64
GeForce GTX 460 1GB | X-Fi Ti Pro | A8N32-SLI Deluxe | Antec P182