The HP 530d CMT has an AGP expansion slot for graphics. Many will tell you that AGP is dead and there is no use in attempting to upgrade. They are wrong.
The highest performance AGP card available is the HIS AGP 3850 TURBO with iceq cooling. It works in this machine. I know because I have one installed in a d530 CMT. THE HIS AGP 3850 turbo is rare and difficult to find. But it is the tippy top of the line for AGP graphics. You can't do any better. Check ebay periodically. They show up occasionally.
Also available are 3850 cards from Sapphire and PowerColor but neither of them quite match the HIS turbo version. HIS also released a non-turbo version (not factory overclocked) but it also is rare.
Alternately you should be able to install a new AGP ATI 4650 currently available on Newegg for under $100 US. For brand new, you can't do any better. 4650 will likely be the final word for for AGP graphics. The 3850 is the better choice, however.
You will have to upgrade the power supply as well, which is problematic because HP did not conform with with ATX standard power supply configuration. I use a corsair TX 650w power supply for my machine but had to do some case modifications to make it work.
It plays blu-ray movies flawlessly. BTW, this machine also has 2 SATA controllers so modern disk drives and optical drives are compatible with it.