Thanks everyone for the great inputs. Interesting that no one commented on the component actually standing vertically. However that tells me that keeping it cool should be my main concern. I think I will try to put a stand on the side and not get too cute with space saving.
The first post answered the question, and I agreed with that first post, beyond that, it was important that you also focus on the importance of properly ventilating the receiver when you do have it put in place, as poor ventilation is a far more serious newbie mistake.
That is: Q: "Can I put my receiver vertically?" - A: No.
Okay, well then I'll just tuck it into this enclosed area with no ventilation instead.
WAIT! You can't do THAT either!
Very important that both items are met so that you get years of use from your system without any problems.
With the big push to get things as thin as possible like TVs, and speakers I am wondering why receiver manufacturers have not made components that stand vertically to save space and design them to keep cool in that upright position.
I would be a buyer. Imagine what cool things could be put on that large surface area. A family of components would be needed so that all of them are vertical.
Just thinking out loud.
There's actually practical reasons for this. Mostly it deals with the fact that heat rises. So, a component that is laid flat, over a large area, cools more effectively than a product which is put sideways. The heat would rise up through the other components and overheat towards the top.
There is no real space saving from any design, as a 18x18x7 inch receiver is still that size no matter how you put it. But, while it WOULD be nice if components were more flexible with their orientation, since they are not, the option is to find a place to put them where they aren't intrusive in your space.
For example, my A/V receivers (more than one) are in my basement storage area. They are well ventilated, and the wiring goes from where they are, up to my family room and to the rec room. They are controlled with a very reliable RF remote control system. My wife never sees the receiver, and I get the benefit of the nice surround sound system.