@mikeymike
WTF


An A500 is as far from AT as one could get.
AT only offers a hole for the KBD-connector, the A500 will need a full row.
AT is deeper than wide, the A500 is wider than deep.
AT offers 8 slots, in a right angle to the mobo, the A500 has 2, inline
with the mobo ....
Back to the topic:
Yes an A2000 can fit in a big-tower, but it does require some work.
(had mine converted for several years)
You may have to move the PSU, to keep the video-slot accesible, and
you may need to sacrifiy some of the 5.25" drive-bays (depending on the case).
The board is 42cm wide (thats a bit more than full-size AT),and 36 cm
deep (standard AT-size).
Another problem will be the slots, as the Z2-slots have various ports
below them,and as the Turbo- and Video-slot use non-standard
(plain) brackets.
I simply removed the backside of the tower, and replaced it with the
one from the A2000.