Alright, have you tried SetFSB? It works on some OEM computers. It is pretty much a overclocking program. If you can get an OK overclock out of your computer you may not have to buy a new CPU at all. I wouldn't spend 185$ or w/e that wolfdale is simply because its
an upgrade. Save your money buy a new mobo that supports your CPU plus the one you want to upgrade to. Going the i3/i5 route right now is pointless, they are crap, they don't OC well they are going to be phased out by Q3 2011 and they just don't give a huge increase in performance over 775 to justify the price.
Here is a 775 mobo that should support your current chip and will overclock it.
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128372 You can run Linux for free or try and get a copy of Windows through MS's student program, or even just buy a new one. You can get W7 new for 99$ on the Egg and you still come in under budget. Buying a new CPU isn't the smart way to go. Buy a mobo overclock your CPU and if you don't get the performance boost you want you can sell your CPU and buy a quad.