For a system using a single GeForce GTX 550 Ti graphics card NVIDIA specifies a minimum of a 400 Watt or greater power supply that has a combined +12 Volt continuous current rating of 24 Amps or greater and that has at least one 6-pin PCI Express supplementary power connector.
The HIPRO HP-W531HF3 530Watt power supply unit that was used in the Intellistation Z Pro 6223 has a maximum combined +12 Volt continuous current rating of 34 Amps and has one 6-pin PCI Express Supplementary Power Connector. The rail labelled as +12VD ===/ 14A is most likely the one that is used for the PCI Express Supplementary Power Connector.
Power wise you are fine.
Have you tried clearing the CMOS to allow the motherboard to re-enumerate and reallocate resources for the hardware change?
Do you have the latest motherboard BIOS version installed?