New Macbook Pro 15 inch - using SD card as storage ?

Thinking about selling my late 2011 macbook pro (2.2 i7, 4gb ram, 500gb hdd) and getting the new macbook pro 15 inch - would it be possible to just get the 256gb solid state drive and then get an SD card and use that as storage? I'm talking about storage for applications, etc. not just a few word documents or small stuff - I mean like a +/- 100gb one - would this be okay?

also - how much do you guys think I can get for my old macbook pro ?