Keep in mind that Memory and Storage Space are two different things. With lot's of images (in RAW format) and music files, you will want lot's of Storage Space, at least 500 GB, 1 TB if you can (or anything in between). A good amount of Memory (RAM) will be helpful when running your applications (music players, photoshop, etc) and manipulating your images.
As for Re-certified computers, they may actually be better. Most PC's are built on an automated assembly line and are never touched (or seen) by a human. The re-certified ones are ones that were returned for some reason, so a real live person had to inspect it, fix anything that was wrong with it, and make sure it was working properly before allowing it to be reboxed and put up for sale, at a discounted price even.
If I may suggest, consider getting an external hard disk drive to keep back-ups of your images. Can also be handy if you ever need to transfer a huge number of files from one computer to another.