I've got a pre-built HP Pavilion Slimline S5710T System
PCI-e 1.0 slot motherboard (H-IG41-uATX)
Intel Core 2 Quad Q9550
4GB DDR3 1333 Mhz Ram
AMD Radeon HD 6450 (Low Profile)
400W PSU (TFX12V) (No PCIe power connectors) (I could get a 400W PSU With a 6 Pin Power Connector)
I'm looking for the best card for this case, I don't mind full height as I could mount the video card outside my case as well (with modification and PCI extender).