Fixing my Q6600 -- Looking for tips

Hi there.

Two years ago I bought a new computer and at that time it was the answer to all my prayers but lately it has begun to lack that extra "uumph!". I've therefore decided to take the necessary steps to get this computer as up to date as possible without having to ditch a whole lot of parts.

One of the main issues I am having is the temperature. With everything on stock speed I am getting these readings;
Idle -- Actually, writing this post;
RealTemp: 55C
Hardware Monitor: Core#0: 61.0C, Core#1: 60.0C, Core#2: 58.0C, Core#3: 55.0C

When running a game, such as Trine it goes up to about 70C which I have come to understand is too much? This basically eliminates any attempt at overclocking.

Current specifications
CPU: Intel Core 2 Quad Q6600 @ 2.40 GHz
MB: MSI P35 NEO-F
RAM: 2x TWIN2X 6400 DDR2, 2048MB CL5
GFX: XFX GeForce 8800GTX 600M 768MB XT GDDR3
PSU: Fortron/Source Epsilon 700W

I have a huge computer chassis so fitting new components in shouldn't be a problem; Cooler Master Stacker 831 Black, 2x12cm

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I have read some great reviews on the ThermalRight Ultra 120 Extreme but I'd love it if any of you would be so kind and help me out with what I should get to solve this problem of mine.
I'd like to upgrade my graphics card as well and OC my CPU even if it means I need to ditch my motherboard. I guess I should also get some thermal paste?

All tips are greatly appreciated. Thanks.

Forgot to mention I'm using a resolution of 1920x1200 pixels.