Your specs don't seem that low to me, but maybe that's because mine on my desktop are far lower 8)

2.4ghz processor should be pretty good for you still yet right now. I wouldn't upgrade to another p4; you'd be better off waiting for a core 2 duo (or even a 4 core or 8 core >;D) to become a viable option.

Ram would be the crucial thing to upgrade, I think. Most people seem to be recommending 1gb ram these days, and it would be a good idea that if you had them in two different sets that they were a matched pair. The ones that you listed should do well for this.

and of course a disclaimer; i am pretty unknowledgable about parts stuff, so wait for yams or samuraid or someone to come by and verify or discount any of that.