What can I do to make this a better machine?

You should have given info on what you use it for ! Would be easier then. Well, I really hope your ust trying to show off. Its obvious, those stats are very good ! I dont really know what your lacking their, unless your a hardcore gamer, graphic artist, autocad programmer(or the like) If your using it for internet, music and video. You really dont need much else;

However, the best thing to finish off a good system is a damn good graphics card. They are very important ! Control your gui, video, screen colour, gaming.. etc etc..

So get a good graphics card !
Get a bigger HDD !!
Get a faster DVD drive !! Or upgrade to a HD DVD drive!!