Owners of PMG5 aiming to install the most powerful graphic card available for this hardware, aka Radeon X800 XT, can simply not find it on the market, already last december supplies for this card were really low.
Yesterday a reader from XLR8yourmac reported his adventure while attempting to purchase one unit from the ATI website for more than 6 months The RoHS directive might be responsible for such supply shortage as ATI might have problems to replace component not RoHS compliant. At the end, ATI might decide not to further manufacture Mac Edition of such old graphic card models (small volumes, small margins).
[translation by Linathael]