If I understand what you are planning, your new cabinet will be closed on the top and sides, with doors in front. Keep the back as open as possible and place the back of the cabinet at least 2 inches (5 cm) away from the wall behind them. If you keep the door open, you will have an open path for hot air to escape and fresh air to enter.
Yes, the idea was to have closed sides and front. The rear end would be open. I could place the cabinet a few cm away from the wall, which I would probably have to do for cabling anyway, so that can be done. But I imagine I would still need fans installed, or just leaving it as is would suffice?
I could ask my carpenter to make slat-type holes in the bottom of the cabinet, where the equipment will be, but I doubt that would do any good.
Edit : perhaps I could make slat-type holes in the top of the cabinet towards the back. Then I just have to place the receiver towards the back of the cabinet, so the heat rises. I'll have a center speaker on the cabinet (Paradigm CC690 which is massive), but that will be towards the front edge of the cabinet, so the holes won't be visible.
Just a thought, might work.
Another important thing is to know how hot your electronic gear gets while in use. How do you store your gear now? Do they get noticeably hot as you now have them or do they become only lukewarm?
I have no idea.
My equipment is still in their boxes. I'm moving next month into my new place. However what I can tell you is that I won't be blasting music or watching movies at very loud SPL, at least not on a consistent basis. Most of the time the levels on average will be 65-70 dB.