Sandy bridge processors run cooler than Ivy Bridge which allows them to clock a few hundred mhz higher BUT Ivy Bridge processors are a bit faster per clock so the difference is pretty minor.http://www.tomshardware.com/reviews/ivy-bridge-overclocking-core-i7-3770k,3198-8.html
Here's a link comparing a 3770K @ 4.5GHz against a 2600K @ GHz.
As you can see the isn't a significant difference.
What i recommend you do is save up some money and buy a Core i7 2600K.http://us.ncix.com/products/?sku=57960&vpn=BX80623I72600K&manufacture=Intel&promoid=1371
It's quite a bit more expensive than the Core i5 processors but it's worth every penny.