My suggestion would be for you to determin which you need more of. Storage or the ability to run more, smoothly. My girlfriend has a 40GB hard drive, of which she currently uses about 5-8GB. She's in school so works on and saves lots of documents and other projects. She also has like 5-6 different apps open at once (Dreamweaver MX, Photoshop, several instances of IE, etc) so she needed more RAM. I, on the other hand, wanted more space to store my MP3s and videos, so I went with the hard drive space (between my 2 PCs I am up to ~678GB) so I bought hard drives first, than upgraded to RAM later.
\Dan