Just out of interest why do you want a "stealth" rig?!
I wondered that myself but wasn't sure about asking. Especially since it can be as loud as needed, why is 'stealth' such an issue? Seems contradictory, but to each his (or her) own
Openly Admitting:
So I got a couple of servers @work (smtp, dns, etc). I want to
extend the services those computers do to mining.
I also do not want anybody get suspicious about them having 3-4 GPU's sitting inside. So I want to make them look normal and mine with them.
It seems like every few weeks we get someone on here looking to steal electricity from their employer to mine Bitcoins. Not only is this ethically wrong and also illegal, it will most likely get you fired. And for what, a few measly bitcoins?
People have been fired for this. People have had their lives ruined by this. Please think long and hard about the risk/reward ratio here. Realistically, even with 4 7970s, you'll make about .1BTC a day (difficulty is going up, so this number will be going down, not staying constant). So in a 30 day month, that's 3BTC (maximum). The next month will be less, and so on.
Is risking losing your job really worth an extra $300 a month? Wouldn't it be easier to just ask for a raise?
Not to mention that what you're trying to do is infeasible anyway. No way in hell you're gonna get 4x7970s properly cooled and quiet in a server enclosure. Even if they're full tower ATX size cases, it's still gonna be tough. On top of that, any given server will not have a big enough PSU to support those GPUs. What are you gonna do, switch out the PSUs with beefier ones? And most servers have 1 single PCI-E port if they even have any. So are you going to install a second motherboard in the existing server enclosure to support your graphics cards? Impossible to fit.
The hardware isn't there to do what you want to do, and you'll get fired in the end anyway.
Think about this: you're looking at a spending over $1000 in hardware to try and scam your employer. Does that sound like a good idea? Does that sound like it will end well?
But if you do go through with it and manage to pull it off, keep us updated, because mining rig setups are interesting.