A working 925XE board with a passive northbridge cooler AND 1GB of DDR for $25? That seems like a pretty logical "win" to me, if you have the $25 and time to go pick it up.
Newegg indicates that it supports Pentium 4, Pentium 4 Extreme Edition, and Celeron D - that'd probably make the best choice CPU for it an argument between the 3.73GHz EE, 570J (3.8 1M), and 670 (3.8 2M). Here's a benchmark on Hexus that compares the 3.73, the 570J, and 660:
http://hexus.net/tech/reviews/cpu/1007-intels … -373ghz/?page=2
And some more from HotHardware with game tests:
http://hothardware.com/Reviews/Intel-Pentium- … essors/?page=11
Why do I bring up the EE? Because a quick look on eBay reveals they aren't much more than the 570/670 chips (they're around $40-$50 from what I quickly looked up, with the 570 and 670 being around $20-$30). There's also the novelty/coolness factor of owning an EE - the "king" of NetBurst chips. At least imho.
Of course you could go with a cooler running Celeron D if you didn't need absolute breakneck performance and/or wanted to quiet things down.
Personally I'd say its a good buy if everything works as advertised - NetBurst chips are a dime a dozen, so you have loads of options for making it into a working system on the cheap, and it has a nice mix of I/O capabilities - supporting more modern hardware (e.g. PCI Express and SATA) as well as older stuff (e.g. Parallel and ATA). It also looks like the 925XE will support Windows 98SE (it doesn't appear to be past the cut-off) along with XP and Vista/7. So that gives you heaps of options for where you want to go with the build.