Various BSODs and freezes on a newly built Windows 7 PC - 99% hardware

I got various BSODs and freezes on a newly built Windows 7 machine.
The problems started immediately before installing windows. I got the first freeze the first time I entered UEFI BIOS. After that I flashed the latest BIOS, after which I managed to install Windows 7. Once I did, I started to get the BSODs and freezes.

I tried following;

1. reinstalling windows
2. checking all the cables and connections
3. reseated the cpu and changed the thermal compound.
4. tried with 3 different RAM models
5. tried with different GPU
6. tried different HDDs
7. tried different SATA cables.
8. checked temperatures which seem to be fine.
9. cleared CMOS via jumpers and battery.

In my opinion, the only culprits could be;
1. PSU (new Corsair VS450)- too weak!?
2. motherboard - some kind of a hardware fault!?
3. case - new Cooler Master CM Force 500 - some kind of a hardware fault causing problems with motherboard or PSU?

The reason why I'm mentioning the case is that at one point I thought the freezes were triggered by inserting the USB stick into the USB drive, but I even got freezes without it, so I guess it's not it. Although I thought I should mention it.

This thing is making me crazy. I guess the BIOS freeze should point out to hardware fault. I have a terrible dealer which will charge me for testing each component individually, so I have to send the right one in for RMA. Unfortunately I can't send the whole case for testing. So please help me finding out which part is faulty.

The fact that you froze in bios is unusual, so its obviously a hardware problem unless your bios itself is bad. You said you reflashed it already so the bios is probably okay, however you might try flashing in DOS if that's not how you flashed before. Aside from that, I'd try booting into Hiren's Boot CD or UBCD and playing around with their programs for a while with a hardware environment of a different psu, no hard drive at all, just one dimm, and the slowest video card you have. Doing this removes the burden of dual channel memory timing, a potentially bad hard drive, the power burden of a high powered graphics card, and windows. If you are stable doing this, you can then slowly add back in your components and note which one causes problems.

But if you are not stable in this minimal environment, I would remove the cpu then inspect both the cpu pins and the cpu socket very closely with a magnifying glass. If it looks perfect, do the same with your dimm sockets and your dimm pins. And if they are perfect, you probably have a bad motherboard.