I can promise you that you have to get a new mobo if you want to get a Tbird.They are SocketA CPU\'s and will not even fit in a mobo other than a socketA mobo (also known as Socket462),they also need a special chipset (AMD750,VIA KT133,VIA KT133A,AMD 760 etc).
RAM is very cheap know adays so that is always a good buy.
You have said before that you needed a new HD.
And you don\'t need a GF.2 ULTRA they are about 495$ (last I knew),you\'ll be fine with a GF.2 GTS,but I would wait till the GF.3 is officially launched,the prices of GF.2\'s will fall.