I'd have to go with my Phoenix expansion box for my A1000. This gave me 2 ZorroII slots on my A1000. First I plugged in a 2058 Ram card - that let me install my bootup stuff to RAD for quick rebooting even before I got a hard drive... Then I added a Trumpcard with a surplus 52MB Quantum drive... wow! such space. :-)
The Video Toaster gets the nod on the 2000 end. It's just too cool, even though I don't have much use for it myself..