Holy mother! If you go the DIY route, you're talking more than $400 for just the lumber in that unit. That looks like cherry or walnut, and a big wall unit like that eats up board feet fast! It would really surprise me if that Diamond Case is less than $4,000. In fact, I've seen prices online for their TheaterTech line (smaller than the unit you're looking at) in the $3,500-$4,500 range. Remember, they're called DiamondCase Designs, not CubicZirconiumCase Designs
DiamondCase makes truly exceptional furniture for people with truly exceptional home decor budgets. If you don't have that kind of coin lying around, you could build *something* like that unit for less than $1,000 in materials. Then, you'll spend a massive number of hours sanding, staining and polishing that wood to achieve the kind of finish quality you see on the DiamondCase stuff. Not impossible, but if you don't have the tools and a work area for the project, then it might be impractical to attempt yourself.
You can spend less than $1,000 on a pre-manufactured wall unit, but most of those use icky MDF with a fake veneer. Here are some units that I found on an earlier search, and bookmarked:
http://shop.store.yahoo.com/epop/medbridwitsi.html
http://store.yahoo.com/furnakit/su-4675-275.html
http://store.yahoo.com/hfsn/larscreenenc.html
http://www.everythingfurniture.com/cithomtheatf.html
If you don't have anything against fake wood, than these units above might suit you well. I decided against one because I didn't like the one-size-fits-all area for the TV. So I designed my own plan and will build it in the fall:
http://extranet.digitalspinner.com/ht/ecenter.jpg
The Amish suggestion is a good one... You could also look for other local craftsman to build a custom unit for you, using cheaper wood (pine, etc) to lower the cost if you have a low budget.
Sean.
