With buses, ports, security systems and power requirements changing all the time, at my work place we've mostly just given up on upgrading PC's, as the manufacturers want us to do. In my lab we try to upgrade PC's once if we can, and then after that further upgrades usually are not practical.have you been replacing your windows pcs completely? that would be ridiculous. the key reason for windows pcs is ugradeability, then you only need to spend 500-1000 every 5 years for a significant upgrade and not 3k all over again