Best timings for mid-range rig

I currently have a Windows Experience Index base score of 4.5 with the memory being the only bottleneck. I have 3gb of Micron RAM.

Everything else is at 5.9 except for my Gaming graphics score, which is 5.4, but thats because its a Zotac 8600gt 512mb DDR2.
I understand that its a matter of changing the timings, but when it comes to timings, I'm a little bit of a noob.

What I have is a stock 300w PSU that is not only powering my 8600gt but also a Q6600 running at 2.4 ghz. So if I increase my timings, would there be a chance of instability due to my PSU?

My current timings are:
DRAM Frequency - 333.3 mhz
FSB: Dram - 4:5
CAS# Latency (CL) - 5
RAS# to CAS Delay (tRCD) - 4
RAS# Precharge (tRP) - 4
Cycle Time (tRAS) - 14
Bank Cycle Time (tRC) - 20
Command Rate (CR) - 2T
Voltage - 1.8 V

These were the timings found in CPU-Z v1.44.2

One thing I noticed was that my current timings were different than the Timings Table found under the SPD tab in CPU-Z which were 5-5-5-15-20 under the 333.3 frequency. Also, I am unable to change my voltage in the Nvidia Control Panel where I am able to change my timings.

Is it possible to increase my timings even though I have an inferior PSU? If so, what timings would be the best for my rig? Would the Vista base score only change if I were to buy an extra gb of RAM?

I want to maximize the gaming experience, and of course raise my memory score in Vista.

My current system:
Acer X223w 21.6" Widescreen
Windows Vista Home Premium x64 Sp1
Intel Q6600 Quad Core @ 2.4 ghz
NVIDIA MCP73 A2 nForce 630i ACER
Zotac 8600gt 512mb DDR2 PCI-E
Micron Technology PC2-5300 1x2GB 1x1GB
Stock 300W PSU


Any help would be much appreciated.