I had an A2000 which I soon put a used A2620 card into -- that was the 68020 accelerator which effectively quadrupled the speed of the system. (When was the last time you saw an upgrade card do that??) It was the same card Commodore used in the A2500. It was an amazing machine for its day, not only in terms of graphics and audio, but for sheer processing power.
The thing that always drove me up the wall was SCSI adaptors. They were always tricky to get working -- fiddling with dip switches and jumper pins on the drives, and terminating resistor packs -- and I never had one that worked for a long time. It seemed like there was a steady churn of companies putting an Amiga SCSI card on the market, then going out of business, then another company would take a whack at it. I think I burned through half a dozen completely different SCSI adapters.