Thanks. I'd seen PCI to PCIe 1x adapters but didn't know 16x adapters existed. New motherboard is a considerable investment - will have to decide how much I want this or if my current setup is "good enough" 
I never got the DMA fix done, so my options are open, at least.
Okay, so it might work (that's a big might).
Regarding new motherboards, Trevor said he was hoping to sell the A1222 board below 400 Euros (
link). More expensive than a PCIe to PCI adaptor, but it's a nice little board (got one myself).
Hans