You said AMD 500. Is that an Athlon 500 or a K6-500? If it's the latter, I'd say wait. A new system will want faster memory so you might end up paying for it twice in the end. Even if it's an Athlon, it probably uses 133 memory and new systems use DDR as mentioned. I'd invest in something you can use in your new machine like a bigger, faster hard drive., CD or DVD burner, etc.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken