Heaver equipment like amps and UPS at the bottom, and lighter equipment as we work our way up. However, the AVR should be at the top of the heavy stuff so you can read the front panel without laying on the ground.

Keep audio and video sources together if possible. If the cabinet is adequately cooled, the stacking due to heat shouldn't be a big issue.

it's like a painting, everyone's is going to be a little different, even if you are trying to replicate the same image. And, each one will get better. Post pictures.