From the ICs you mentioned, only the Gary should get a little warmer after some power on time.
Unless you have have Serial or paralell or Floppy ports usage, the CIAs should be cool.
The ROM IC should be cool as well.
Every video dedicated IC should get warm. So Denise and Agnus should get a little warm. Denise should get warmer of the both.
I'm not 100% sure, but yes, the Gary chip is the same in A500 and A2000. Just compare the code numbers. If they are the same, you can exchange them in these machines.
What is the exact problem with your A2000 ? Completely dead machine ? What's on the display when you do power on the machine ?
