Using SD Slot on MBA to expand storage

I'm trying to conserve the most memory on my ssd as possible with my new 128gb air. I have about 20 gig worth of music, and my idea was to get a 32gb SD card, with a 10-15mbps transfer rate, and store all my music on that card. Is this a good idea, or will it just slow my computer down? It was too far of a reach to get the 256gb air, and I can get an SD card pretty cheap.

I dont have many other things that need to be stored, but Ive read if you load up a ssd, it can actually slow it down to speeds of less than a hdd. I will be loading Microsoft Office 2011, Adobe CS5 Suite Standard (student and teacher edition), and using the computer to complete papers and surf the web. I wont be editing video or doing huge projects with CS5, just working with photos, an occasional website, and so on.