Core 2 Duo E4400 to Core 2 Quad Q6600 worth it for gaming?

I have a DQ965GF (LGA775) motherboard and have been wondering if I should bother upgrading to a Q6600 CPU from an E4400.

How much of a performance difference should I expect from this upgrade? Would it be worth the 90 dollars, or should I just stick with the E4400?

I'm primarily using this computer for gaming(Fallout 3, Fallout: NV, Skyrim, Team Fortress 2), and other miscellaneous tasks such as web browsing and listening to music.

This link contains a comparison of the two CPU's specifications:

http://www.cpu-world.com/Compare/700/Intel_Core_2_Duo_E...

In case you're wondering, here are my computer specifications:

Intel Core 2 Duo E4400
Intel DQ965GF motherboard
Seagate 250gb 5400 HDD
DDR2 667mhz (4gbs)
GeForce GTX 550 ti (1gb GDDR5)
300 Watt PSU
Windows XP Professional, 32bit

It's an aged computer.



Thank you!