You said the secret word. or 2 I guess, NEW CASE takes care of most of your problems. DDR2 RAM will limit your choices some but you can get any 775 socket motherboard (a P45 is best) and everything else will work in the new case. You just need to figure out what cost you want to put into the CPU. a e8400 was good for 2 cores, I have a Q6600 which runs 5 toons no problem. Then there the Q95xx series which is more but is newer and runs a little better than a Q6600.
Hope that gets you a better idea, just go drool through Newegg and check your wallet. Find what looks good and then see if Best Buy has it.