No, the video card ram is not used as fast ram. You're now basically screwed. There is not easy way to get good 32 bit memory on an A3000/A4000 if you accelerator does not support it. You could get a zorro card like the DKB card, but they were about the $200US mark when I was looking at them, *if* someone would even part with it. For that reason alone, I stayed with the 3640 card until I could afford a CSPPC
There are lots of cheap cards out there to add 16bit ram, but remember that your machine is going to crawl the moment you use that ram.