They have both XLR and 1/4" inputs...and they come with a set of cables that have XLR's on one end, and 1/4" plugs on the other. SO...I'm using 1/4" female to RCA male adaptors...then running an 1/8" mini-plug to RCA connectors...from the sound card.
Nothing fancy and they sound amazingly good...of course not as good as my main system...but for $180...not too shabby.