Twin 12v is a definite no-no with the 805. You want a single rail, with good amperage. I think that might explain why youre unstable at 3.8Ghz. Ive got mine running 4.0Ghz on air right now.
Also, upping the PCI-e bus frequency does nothing for framerates or graphics performance. You really need to lock it at 100 (the default), and also lock the PCI at 33.3 when you start overclocking with the P5LD2 boards. At 125, youre really running the risk of frying the graphics card
How do you figure a twin 12v rail PSU is no good for a dual core CPU? PSU manufacturers have been pushing toward multiple rail units for some time now and dual core CPUs are more common than ever.
I have a good 450w PSU with a high amp single rail - it made absolutely no difference to my overclock, thats why I'm using the 375. The 450 is in my gaming rig. I use the 805 for experimentation and video encoding. Incidentally, I dont run it at 125 PCIe, I did that to see how far it would go. PCIe is currently 119mhz @3.6ghz. Its more than likely I've reached the limits of this mobo or CPU.
BTW Cucamel, there is a bug on the VM board - you have to raise the PCIe to get a decent overclock.
I bought the 805 just to see what it can do - will prolly buy another with a different mobo - the full fat P5LD2 looks like a decent candidate. With the CPU costing less than £100, its hardly the end of the world if I kill it. But I wouldnt suggest other people push it too far - Thats why I suggested scr34m should use the onboard gfx for testing.
I do agree with you about Scr34ms temps, they are way too high, even after he fitted the case fan.
 I would expect those temps at full load.
My CPU and mobo temps are 34 and 28 degrees. I have 3 x 80mm case fans and one 120mm. I use a freezer pro on the cpu and 40mm fan on a large heatsink on the southbridge. I also use a heat terminator for blowing air across the RAM. Used a couple of Zalman fan wires to reduce the fan speeds and noise.
Scr34m, I would look at replacing the southbridge heatsink with a bigger, actively cooled HSF, also check the air temp at the top of your case after running the system for a while - see if its warm. You NEED good airflow in ur case if you want to overclock.