I still advocate building your own. Your processor and graphics card are on the older and weaker side respectively, which are the most important components.
It all comes down to what you plan on doing with your desktop, and how much of an additional threshold you want. For example, if you wanted to build a desktop that runs Starcraft II on medium settings, then a
Pentium E6700 and a
240 GT are sufficient.
Having helped multiple high school seniors/college freshmen build desktops, the only thing I can say is that you should try to predict your needs as accurately as possible. Overkill is always better, because even though you will spend more, that still leaves you more options later.