You don't need a new soundcard. You need a new cable though. There's usually 3 types of connectors. One being digital, and then there's a couple of different ones for cables. I have dealt with both of them, the MX300 and the Live have different ones.
Just go down to your local computer place and check for cd rom/sound card cables.
They will probably run you around 10 bucks, unless you know someone that works for a store or they give you a good deal on them.