If money isnt an issue id say go for the 3820 you will get better performance if your not overclocking but your gonna take a hit on expensive motherboards and 4 / 8 sticks of ram for quad channel DDR3. the Sandy Bridge E line is also nearing its end as IVY bridge begins to make its way into the mainstream in Q2. the 2600k would be your cheapest option with the ability to overclock it easily. The performance will be very good regardless of what CPU between those choices. just make sure you throw three snazzy GTX 680's in your rig if u plan to triple SLI
you can also overclock a 2600k to the speed of a 2700k with about 5 seconds of work.