You don't need dummy plugs.
Also, you might wanna get better cards than the 270's. It's going to take you a while to make your ROI with those cards.
What GPU then? ROI calculations say under 3 months, so not bad. IF there is a way to improve that, I be glad to hear. Why do I not need dummy plugs? Running Ubuntu if that helps.
Go with 270X HIS cards from newegg.. they are around $200 bucks. Dump the SSD and save the money. Grab a USB thumb drive and load SMOS linux on it for free. Get a Gold rated power supply, dont skimp here.. Newegg has good ones for decent $$$.
Running Ubuntu so mining OS are out of the way as im using a wifi connection with a cheap USB wifi stick. IF there are mining OS that support WIFI or able to run Ubuntu off a USB stick, it be great if you could link it in a future post.
Any links on how to configure multi GPU mining on Linux using cgminer,bfgminer, etc. would be great also!
Gotta go wifi? Have you looked at ethernet over powerline options or even using an wifi ethernet bridge? That's what I use, works quite well. Then you can plug ethernet into your rig, not worry about wifi usb adapters for linux.
As for configuring multiple GPU's.. just download SMOS linux (google it) and run it from usb stick. no special configuration really needed if you follow the simple instructions on their web site.