BleepingComputer.com: System Issues, Overheating CPU?

I have recently been having some problems with my system. I built it about three years ago and it has run great, with a few exceptions along the way. Right now I am having problems with my audio and I think it is stemming from my CPU overheating. The problem itself is that at first my headset would not work at all, so I disassembled the system, cleaned off all the contacts and rebuilt it. Then I reinstalled the Realtek audio drivers. My headset speakers now work, but I can not get the microphone to work. My regular speakers work well also. My system is running at 34°C, but my processor is running at 80°C. It is using the original heatsink and fan that it came with. It has been running fine these past few years, but now it is giving me problems. I am considering replacing the heatsink with a better aftermarket one, or possibly even liquid cooling. Am I headed in the general right direction, or are there other things I should be looking at? I am willing to supply any and all information necessary to get help with this. Here are my system specifications.

CPU: Intel Core 2 Quad Q9550
Motherboard: ASUS P5N-D LGA 775 NVIDIA nForce 750i SLI ATX Intel Motherboard
Memory: (2) OCZ SLI-Ready Edition 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model OCZ2N800SR4GK
Graphics: EVGA 512-P3-N861-AR GeForce 9600 GT 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI
HDD: 500GB 7200 RPM WDC WD50 01AALS-00L3B SCSI
HDD: 640GB 7200 RPM WDC WD64 00AAKS-22A7B SCSI
Case: Antec Nine Hundred
PSU: CORSAIR CMPSU-750TX 750W ATX12V
OS: Windows 7 Home Premium 64-bit
CD/DVD:

I believe you are better of getting a aftermarket cooler.

Agreed with killer. 80c seems high, even for a stock heat sink. You may want to try to re-paste your heat sink, just to make sure the problem was not the seal between the CPU and heatsink. Make sure the heat sink fan is working correctly and isn't spinning abnormally slow -- and check in between the spaces of the metal under the fan on the heat sink, to make sure dust hasn't clogged between the fins of the heat sink.

Having an Antec 900 myself, I'd also advise you to make sure your fans stay clean -- especially the front two that suck in air -- and your airflow remains good. If you haven't installed the optional side fan, it can help to get rid of some of the heat.

It is also possible that the cpu fan may not have been seated properly.