gave up on Mac Mall - bought at Dallas (Willow Bend) Apple Store
With all the stories of Apple Stores having DP2.5s in stock, I called one in Dallas Friday night and found they had at least 6. I waited until Saturday night to get an update from Mac Mall since they said another batch might be coming in, but my order still said backordered. So I bought a DP2.5, a 23" Cinema HD, AppleCare, a discounted .mac subscription for when mine runs out, and an ADC-to-vga adapter to hook up a second monitor. Now I don't have to worry about whether or not Mac Mall would ship to my while I was on vacation.
I used the utility to transfer everything from my SP733 and installed an extra 1GB RAM I'd previousdly bought from Mac Mall plus an updated MOTU PCI-424 digital audio I/O card. After a few hard crashes (forced restart), I decided to part with any previous app installs and configs and reinstall OSX. TechTool Deluxe reported all the hardware was fine.
The OSX installer aborted just when transfer of software was to start, right after the drive had been reformatted, saying something was wrong with the install. After this happened twice I took out the new RAM and PCI card. That seemed to fix it. The reinstall was successful.
Eventually I reinstalled the RAM and starting loading software packages. I kept testing the apps that had previously hard-crashed and finally felt that the system was stable. I installed the PCI card in the top slot instead of the one next to the AGP slot. This seemed to work. There's lots of effort ahead to get this beast fully configured, but I'm looking forward to putting it to good use.
It cost me a lot more to buy it locally (taxes and no discount), but peace of mind can be priceless.