shivang222,
Do you have a wireless home network? I assume not, given your post. If you do, however, I'd lean towards using a Squeezebox, Roku, Sonos, etc. Your laptop can act as the "server"; the above devices then just plug in to your Marantz as another source. Aside from that advice, I'd steer clear of Bluetooth - its range isn't very good, and it can introduce unwanted noise.
If you want to go wired, then you'll want to avoid the on-board soundcard on your laptop. A number of external cards should do fine for your purposes, including some of Creative's offerings.
Personally, I'd leverage your home network if you have one. Even if you don't you might want to consider putting one in place, if only for this purpose. You can get a perfectly good router for $35.