RE: XPS 15 L502X UPGRADE FROM I7-2670QM TO i7-2960XM SR02F
I have the same XPS laptop and I had the same idea to upgrade it (bought mine in april 2012). I think the money you spend for a processor upgrade is not well spend since everything is updated (also the graphics card is not that fast in our XPS). The best thing you should do (If you didn't do some upgrade yet) is to get a Solid State Drive (SSD). That's by far the cheapest and also the biggest speed boost you will get if you don't have one atm. I will get my XPS upgraded with a Samsung EVO 1Tb or a Crucial M500 960 Gb (probably this one, it's slower and smaller in capacity, BUT it's a MLC drive and not a TLC drive (2 bits instead of 3 bits) and it has a better protection system.
Also, I think the new processors are way too power consuming (thus getting too hot on heavy workloads). Check comparisons on www.cpuboss.com.
I hope you are helped a bit with this information.