The case decision was one of the toughest calls to make. My normal tendancy would be to go high end for the case and the power supply. Both the case and the power supply generally have a longer usable life span than many other components. So generally, you can think of the extra cost for these components being amortized over 2 or 2.5 PCs.
With that in mind, I spent a lot of time digging into reviews. There were many attractive cases, but I was leaning towards the Antec P180 and an OCZ's GameXStream 700W power supply. The combo is very pricey, coming in a bit over $300. That's too high for a one time mid tier+ PC build. Spread over 3 PC's it would be much more reasonable.
The low end alternative I was most attracted to was the Antec Sonata II and it's integrated 450W power supply available at Newegg for $89.99...
In the end, this decision came down to timing. Under normal circumstances, I would have bitten the bullet and gone with the high end option. But right now, my guess is that the ATX format motherboards are going to be replaced with the newer BTX format over the next few years. BTX is a slightly larger format so it won't fit into a standard ATX designed case. BTX is pretty rare right now, but it's main point of sale is that it is built around a zoned format that designed to facilitate cooling. With the ever increasing heat problems, BTX could take off, if it lives up to it's better cooling promises.
There are only a few BTX cases or combined ATX/BTX cases out, and I'm not willing to take on the risk of a 1st generation case at the current premium prices.
So, I decided to go with the Sonata II package and pocket the price difference. The Sonanta case is pretty mainstream, but it is solid, well designed and thoroughly tested. The combo is cheap enough that I can afford to upgrade the powersupply downstream, if I decide to go with SLI graphics. For now, I only plan to keep the addons limited, so the 450W power supply will be sufficient. I don't expect to add a second graphnics card for at least 12 months, and by then, the price of an SLI capable power supply will have dropped significantly, and the price of my graphics card will also have dropped. If the Sonata II could be purchased with the Antec 550W power supply, I would go for that without a doubt.
With BTX on the horizon, the high end case and power supply option don't look like good bets.
Choice made, Sonata II. By the way, the Sonata II is a very attractive case. It would have been nice to have a removable motherboard tray. But I'm not going to be in the case tweaking with the guts very often, and it may have added 5 or 10 minutes to the three hour hardware assembly process.