For those of you curious about the wide voltage picopsu, I went that route, combined with a Cooler Master NA90. My original plan was to use an older AC adpater from the Dell Latitude laptops I have around, but unfortunately they use a proprietary plug, and adapters are extremely hard to find, or expensive enough to not be worth buying.
My system is as follows:
Gigabyte Z77-N Wifi
Core i7 3770 with Scythe Shuriken + Noctua A9-14 PWM
2x4GB Mushkin Silverline (1333)
Intel X25-M G2 160GB
I'm a bit annoyed by the fact the motherboard has no vcore adjustment - I wrongly assumed it would given it is Z77, and that my H67 board had it.
Regardless, I attached everything to a kill-a-watt and maxed out the overclocking (non-K CPU, so max 1/2/3/4 core turbos are 4.3/4.3/4.2/4.1, or 4 bins above stock)
It can comfortably run the turbos with 1/2/3 cores. During benchmarking, it couldn't hit more than ~3.8 on 4 cores, and crashed when combined with GPU loading. This is probably the OCP of the picopsu kicking in. Because it does not simply pass through the 12v line, I think the regulation is quite good, and if you look at johnnyguru's review, he seemed reasonably pleased with the wide voltage option. The AC usage peaks at around 90-95W, but typically hovers in the 40-70W range. Idle usage isn't so great, at around 25W. For some reason, I had it idling at 18W before, and I don't know why it's higher now. The only things I recall doing between the two measurements was add the 92mm fan to the heat sink, and swap an i5 2400 for an i7 3770.
Once I capped the TDP in the BIOS down to 72W from 77W, that seemed to do the trick. Now, it can only hit 3.5 on 4 cores. If I had undervolting I'm sure it could do better. My case fans are intakes, and I think that helps because air is blown directly onto the picopsu to keep it cool.
I tried running the Shuriken with only 2 case fans and that caused overheating. Once I added the A9-14, no problems anymore. The (non-big) Shuriken is just small enough that in theory, I could add a PCIe card and clear the HSF. The Big Shuriken will not clear.
So, a regular quad core is feasible, if you limit the power consumption. You won't get your full 4-core turbo, but it comes close, and you can get your 1/2/3 core turbos plus overclocking.
Lone Industries L1: i7 3770, 2x4GB Mushkin Silverline, 512GB MX100, Dell U2412M + U2211H
Lian-Li A04: i5 2400, 2x4GB Mushkin Silverline, 160GB Intel 320, 4x3TB FlexRAID, all on Seasonic x460, hooked up to Sony 40" EX620 + KEF 2005.3 + Yamaha RX-V667