Well you could go to the ATI Radeon 9200 Pro (PCI), which has 128MB DDR VRAM. It fully supports OS 9 and OS X. Its NOT supported by core image though. This card has both DVI and VGA Ports. It does NOT include an ADC Port.
You could also go to the ATI Radeon 9000 Mac Edition. This card can have either 64MB or 128MB and is an AGP Card that will support your PowerMac. This card has an ADC (Apple Display Connector), and DVI Port (includes a DVI to VGA Adapter) on it.
Both are very good choices for a PowerMac as old as yours. You'll see quite a difference in graphics compared to your stock 16MB or 32MB ATI Card.