I'm really not that sure you'll be able to run a 2600K at 4.8ghz from a 150w Pico-PSU. A rule of thumb (approximation only) for overclocked power consumption is:
Overclocked Wattage = TDP * ( Overclocked clockspeed/ Stock clockspeed) * ( Overclocked Vcore / Stock Vcore )^2
Even assuming you don't have to raise the voltages at all, the CPU itself could be pulling ~ 135w, leaving not very much at all for the rest of the system. I'd be impressed if you didn't have to raise the voltage at all, though. I'm also not that sure you'll find Z68 chipsets on Micro ITX boards (although I hope I'm wrong there). ITX boards don't tend to do too well with overclocking due to the reduced size of the power circuitry.
I can't think of any case which allows for a large CPU heatsink without associated peripherals such as 3.5" and 5.25" bays. Possible options I can think of include:http://www.newegg.com/Product/Product.a ... 6811163177
Silverstone FT03 with a suitable cooler + PSUhttp://www.newegg.com/Product/Product.a ... 6811163169
Silverstone SG07 (comes with 600w PSU) with a down-blowing CPU cooler.http://www.newegg.com/Product/Product.a ... 6811112281
Lian Li PC-T1R (just because it looks awesome, and supports ITX + big PSU + no height limits. Not practical as such, but eh