Not to try to sway you away from buying those but as a former user of KRK I thought I should just let you know that you can get HS7's which are a bigger and more importantly FLATTER monitor for less money. I got rid of my KRKs becuase they're too hyped in the low-mids. These are much more honest and will give you better results.
If the KRKs are the ones you really like go for it, just thought I'd contribute my experience with them.
Also, snaxe is completely right. I believe those have balanced inputs so you will need balanced cables (TRS or XLR) and an audio interface to reduce any noise.
Hope this helps!