Well, upgrading the platform would be more than $300, but the biggest thing I see is the monitor. That's pretty tiny by today's standards. I've seen 23.5 inch 1080p monitors running $160 and less, even with LED backlight. That would leave enough to get a 60 GB SSD, although I would personally get one of the Vertex II SSD's in the 100-120GB range. They are running about $2/GB which while its not ideal, its better and I think well worth it in terms of system responsiveness. I was a naysayer for a while..until I bought one and now I can't see going without one.
Definitely look at some monitors.