Go to your local store, if they're any good, they'll be more than happy to meet your needs if you tell them what you're trying to do. Online I can see cards from 10 $/€ upwards - there's some really nice kit for around 50 - anyway it's up to you.
I would imagine most if not all external sound cards will have the option to record directly from them but you should check with the vendor before you pay.
Good luck and maybe post back what you ended up with and if it's any good.