8K Budget
If you have a $8K budget what gear will you pick for a password cracker (chassis, GPU, CPU, etc)?

I'm n00b in this area.

Thanks for any input, guidelines.
It really depends on what you're trying to do.

Things that matter most:
- GPUs. Buy Radeon 290x cards unless you can get a killer deal on used 7970s (which you probably can't, because Litecoin/Altcoin miners - the cards are worth more now than they were a year ago).
- Power supply. Don't cheap out. The Lepa G1600, while expensive, is probably the best PSU on the market right now for a general cracking system. It's also very efficient, which makes a big difference when you're feeding 1000+W to a system.
- Case. If you're putting it in a data center, you'll need a rackmount case. Otherwise, you could go open air if you wanted, but I generally prefer cases. The Chenbro Tesla GPU case is a nice 4U chassis, and can cool 3-4 GPUs very nicely with a few fan upgrades.

The mainboard needs to have the proper number of slots and spacing. You should be able to do a 4 GPU build for $8k, which will limit you on mainboard options significantly. The CPU doesn't matter as much - I tend to prefer Xeons for ECC memory, but a cheap AMD CPU and mainboard will work just fine as well.

Avoid PCI extenders. They're not worth the months of pain they typically cause.
Thank you Bitweasil! From what I gathered so for regarding the case is that vendors like Tyan and SuperMicro they support Nvidia but they don't seem to support ATI (at least not in writing). Do you have experience with either running ATI instead of Nvidia?
The Tyan and SuperMicro boxes will support AMD GPUs, but setting up the newer systems is a fairly complex procedure.
Thank you very much Bitweasil! Really appreciate your help.
@Bitweasil check out german ebay , much more 7970 then you can handle , caus all the minerga*s move to 280x or 290 and sell out there miningrigs , the last i saw was 10 x 7970 + mb + psu for about 4500€

btT: depends very strong on the things you wanna crack, but for real its never bad to buy some 290x or 290 stock , perfect would be a bundle of 7990 :=)

mb i prefere gigabyte ud7 old one , the new one dont work well with more then 4x6990
More than 4x6990? isn't it bottleneck for driver?
Yeah, latest info on this is that 10x GPU work on X11, however AMD's OpenCL runtime still only supports a maximum of 8.