If you wanted to, you can maybe buy used parts for 4 year old top of the line CPU (that's not terrible, pretty much what my desktop specs are right now is 4 year old top of the line, it's aged rather well)...it'd be more expensive than $70 though. Would require a "new" motherboard and CPU, other than that, your existing power may be usable (depending on if it is proprietary or not and wattage, minimum 400W), you would probably need a new fan for OC, unless you already have one.
i5's are rather cheap on Ebay...2400S is selling for $7.50 right now, though the title says NO RESERVE whatever that means, another one 2400 is selling for $50. Or if you want, there are people selling 2500K which is also really good, you can OC them to 4.3 ish no problem usually and it should run everything great.
http://www.ebay.com/itm/Intel-Core-i5-2500K-2nd-Gen-3-3-GHz-Quad-Core-BX80623I52500K-Processor-/200996754427?pt=CPUs&hash=item2ecc5713fb
Anyway, I recommend you get a 2nd generation i5/i7 that can overclock if you want a cheap CPU and can afford electricity. They overclock really well compared to 3rd/4th generations (more or less on par with the newer stuff in regards to gaming according to Tom's Hardware) with really cheap $30 after market coolers. They do use double the electricity of 3rd/4th generation i5/i7s, but it's not that big of a deal for desktop.
i5's are rather cheap on Ebay...2400S is selling for $7.50 right now, though the title says NO RESERVE whatever that means, another one 2400 is selling for $50. Or if you want, there are people selling 2500K which is also really good, you can OC them to 4.3 ish no problem usually and it should run everything great.
http://www.ebay.com/itm/Intel-Core-i5-2500K-2nd-Gen-3-3-GHz-Quad-Core-BX80623I52500K-Processor-/200996754427?pt=CPUs&hash=item2ecc5713fb
Anyway, I recommend you get a 2nd generation i5/i7 that can overclock if you want a cheap CPU and can afford electricity. They overclock really well compared to 3rd/4th generations (more or less on par with the newer stuff in regards to gaming according to Tom's Hardware) with really cheap $30 after market coolers. They do use double the electricity of 3rd/4th generation i5/i7s, but it's not that big of a deal for desktop.