I think we have some terminology problems.
CPU - Central Processing Unit - is the actual computer chip - the processor
PSU - Power Supply - gives power to your system
The HP mini units previously discussed, are full systems including the CPU, PSU, Motherboard and integrated or discreet graphics.
It seems you need a case, motherboard, and PSU so that you can use some of the parts you already have.
Is this what you are requesting help for or are you looking for a pre-built system that will let you use your GPU?