How can I overclock my system more?

I have:

Aspire case: http://www.newegg.com/Product/Prod [...] 6811144128
here is my Zalman CPU fan heatsink: http://www.newegg.com/Product/Prod [...] 6835118115
Intel Core 2 Duo E6600
Asus p5b deluxe wifi-ap
nvidia 8800GT 512MB PCI-e x16
Corsair XMS2 DDR2 2GB 5-5-5-18 stick and 2 x Corsair XMS2 DDR2 1GB (overclockable to 4-4-4-12 but running at 5-5-5-18)
2 80mm fans sucking in front near hard drive bays, 120mm fan in back pulling out, 120mm fan on side pulling in, CPU fan same plane as side fan blowing out (so the CPU is blowing air off cpu, side fan blowing in cool air and then back fan pulling it out) and PSU fan doing whatever it does.

I have the processor overclocked to 3.15GHz with the highest multiplier and it runs at about 45C idle and if I run orthos for 8 hours it stabilizes at 55C. The max working temp for a Core 2 Duo E6600 is 61 and the "hot" range is around 55. So basically I am right at the limit. I can't get my system stable if I do more than 350-400MHz FSB but if I go lower or higher than that it does. If I go as high as 400MHz though the CPU is at 3.66GHz (stock is 2.4GHz and 32 or 37C idle, I can't remember) the processor will idle at about 55 or a bit higher and will be around 67 with orthos after 15 minutes or so.

My nvidia 8800GT 512MB runs at about 50C idle. My motherboard runs about 30C loaded I am almost completely certain.

How could I overclock the processor more? Could I overclock the 8800GT, I don't want to have to upgrade my card yet. Also, my RAM is rated for 800MHz stock so if I go higher than 400MHz stock I guess the RAM is overclocked right? Is that recommended or should I drop the CPU multiplier (I'd prefer to get the CPU clock as high as I can though). I tried dropping the multiplier to 8 when I was doing 400MHz and it didn't show a change in RAM clock, is there any reason for that? I suppose I could also buy some more Arctic Silver, clean off the processor and fan and re-apply it as it is 3 years old.

Thanks.

i have this feeling since he didn't say what voltage he was using, he left it on auto