REAPER-Nam

Yes. Manufacturers often include a fake plug to do this anyway. My EVGA G2 came with one to test the power supply. They are most commonly used to test custom loops with the PC off.
 
EDIT: If you don't have a plug you can use a paper clip

For mining the pcie lanes dont mean anything, proper mining rigs run off of all the x1 slots too, with 0 performance difference, provided it isnt pcie gen 1

It's a little late for the Ethereum bandwagon! I have 2 rigs running about 2 months now for cheap currencies and now since the market for those went from a few fraction of cents to 6 usd in that time frame. Lets say this I have enough to buy a luxury car or Muscle Car ( Dodge Hellcat ) if i wanted to now, but i'll hold out for something I really need.....A HOUSE! Im using my old R9 290s ( 3 of them). Prices of those cards have inflated exponentially. look for other coins to invest in or mine.  

i sort of disagree, get the 8 gig stick as you'd be less limited in expansion and will still give excellent performance without bottlenecking (even though the ram is the bottleneck in the build, if possible get a 16 gig dual channel 8gb sticks which would put your build at 900. I know that it is tough to put in extra cash for it, but it is the best option for saving money in the future.