There is a good set of reviews of several Sandy Bridge processors, with benchmarks, and comparisons to other Intel and AMD processors here: Intel Sandy Bridge Review | bit-tech.net
I was interested in power consumption. Here are the results for various processors at standard clocks and overclocked, at idle and at load.
The hardware used was:
* ATI Radeon HD 5870 graphics card (Catalyst 10.11 WHQL)
* 2TB Western Digital Caviar Black hard disk
* PC Power & Cooling Silencer 750W PSU
* Asus P8P67 Intel LGA1155 motherboard
* Asus P6TD Deluxe Intel LGA1366 motherboard
* Asus Crosshair IV Formula AMD Socket AM3 motherboard
* Gigabyte GA-H55M-UD2H Intel LGA1156 motherboard
* 4/6GB (3 x 2GB) Corsair 1,600MHz DDR3 memory (CL9)
* Titan Fenrir TTC-NK85TZ CPU cooler, except for LGA1155 systems where we use a Corsair H50 due to the incompatibility between the Fenrir and Asus P8P67 motherboard
234 watts at full load for the most expensive model (i7-2600 K) at max overclock (4.85 GHz), with a Radeon 5870. The same system at the same overclock at idle uses 81 watts.
Without the overclock (3.4 GHz) on the same system: 156 watts at load; 77 watts at idle
The less expensive i5-2400 at max overclock (3.99 GHz): 154 watts at load; 77 watts at idle
The i5-2400, without overclocking (3.1 GHz): 142 watts at load, 75 watts at idle.
Looks like a 350 or 400 watt power supply is easily enough with a single 5870 graphics card, even overclocked.