I made the switch from a fat-backed TV to a wider, slimmer plasma and soon followed with an upgrade for my amp and speakers - the plasma looked ridiculous on my old entertainment unit and the new amp didn't fit.
To give you an idea of how big the new unit is, the TV in the picture is 50 inches. It hung over the ends of my old unit (as seen in the coffee table Instructable).
So it was time to make a new entertainment unit. This would be my first serious attempt at wood work. The most I had done before this was to repair or update existing furniture.
It had to fit my new centre speaker, contain storage and ventilation for my amp and I wanted the cords to be (relatively) easy to get to.
With nephews and nieces running around, I also wanted to protect the gear from prying, poky fingers.
After a few hours of thinking and several sketches, I came up with something along the lines of the pictures below - which of course morphed as I worked on it.
Because your design should match your individual needs. I haven't included exact measurements for every little component of the unit I made.
The point is really to illustrate that you can and should make a custom unit to suit your gear and maybe save you some money that you might have otherwise spent on one of those laminated modular units.
You should end up with a piece of kit that will last you for many years to come - and what's more, if you ever dent/scratch/damage it, you will be able to repair it!
I hope it will serve as inspiration for your work and I look forward to seeing your results!
PS> I am Australian. We use metric measurements and spell words like centre, metre and generally use "ise" instead of "ize". So you will see a bit of that.
Here's a site that might help you ye-olde-worlder's measure stuff *cheeky grin*