If you are lucky enough to ever find one get an ICD Trifecta EC 500.
It's an A500 IDE controller that connects to the side edge connector. It has good styling (same shape as A500) and it has 8Mbyte FAST RAM and is the fastest IDE drive for the A500 reaching peak speeds exceeding the Zorro theoretical limit of 3.5Mbyte/sec using "hidden DMA transfers"!