Here is what i did once before.
i took one of those prefab wooden TV stands you get at Walmart. I removed the center shelf which also fitted perfectly over the entire back of the unit which i later cut as needed.
I cut out a piece of plexiglass and fitted it over the entire front. I also cut out power button and OPtical drive holes.
I put all the PC guts inside, using a mobo tray from another case.
I cut out fan holes in the back. Far left side for intake, far right for exhaust.
I painted the back side of the plexiglass black. So it has a dark mirror finish from front.
Set my TV on top.
wish i still had pics, but after i was done, it looked really nice and modern. I had all the size i wanted without making anything obvious. I could have also put inside it, my Reciever..etc and just use the remote to control everything, or make the front plexi open like a door.
only downside is it was really heavy, but you can make it so that everything fits inside, yet is hidden while still leaving the available space for air flow.
but use your imagination, don't limit yourself to a 3rd party case.