I need your help I have the Mac Pro 1.1 2006 23GB Ram, 2TB HDD and 240GB SSD I'm planing to change the processors from 2.66 Ghz to Intel Xeon X5365 3.0 Ghz LGA quad core CPU SLAED 8M/1333 I have the original GPU Nvidia 7300GT, it works great with OSX Lion but i get waves and it is slow on Mavericks and Yosemite. I guess i need to change GPU, I need your suggestion on that. What GPU do you recommend. If possible i wish to run OSX Lion from time to time because i have apps that i do not know if i can transfer them to Yosemite, can i leave the existing GPU in and add a second newer GPU? or I can only have have one GPU. What is the best GPU that can run Mac pro smooth right now with Yosemite? Thank you in advance for you reply.