Check your actual plugs, but according to newegg., you only have 1x 6pin and 1x 8pin cord. The Vapor-x Version requires 2x 8 pin connectors, so sadly, You'll have to settle for this version unless you want to upgrade your PSU:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202046
Most OC'd 280x's require 8+8 pins. Almost every $300 280x right now (keep your eyes on the gigabyte version) can be used by your PSU, but I'd recommend not overclocking anything in your PC since you're cutting it close. When you overload a PSU too long, it can short circuit and often takes some of your PC with it. It worries me a bit more since RAidmax are more succeptible to this, but since yours has already lasted about a year, If you treat it right, you shouldn't have any troubles. Add CPU wattage + 250w for the 280x + 65w for MOBO + 10w each HDD + 20W for Fans and ETC functions, and thats your PC's max usage. If thats lower than 500 or so, you might be alright.
If this is over 500w or so, I'd think about getting a new PSU. Order the card first, take it slow, and see if your PC has any random shutdowns with the new card in. If it does it once or twice, I'd keep it out and replace the PSU.
I'd aim for 650w if I were you, as it should have a little headroom for your components. Aim for a Corsair, Seasonic, XFX. If you buy a better PSU at the same time, you can buy a Vapor-X like you wanted.
If you have one picked out, send me the link if you are unsure about its connectors/power/quality. aim for 650-750, since a lot of them are in the same price brackets.
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