"xSeries systems can provide a complete migration environment, which systems ranging from uni-processor IA32 (the xSeries 205) to IA64 (the xSeries 382 & xSeries 450) to 32/64-bit Opteron (the eServer 325)." Ref: http://www-1.ibm.com/servers/enable/site/porting/linux/xseries/
There are 408 hits on google for the phrase 'xSeries 325' that isn't supposed to exist.
As you can see I'm more than a bit intrigued that I couldn't find you a better quote - I did see it in a much more definite form in an IBM whitepaper about two and a half months ago. Can't find it anymore though... Had a discussion about it too on the yahoo, but yahoo search doesn't go back far enough anymore. From looking at IBM's webpage it does look like they're now carefully avoiding calling the eServer 325 an xSeries product. I've got a rather clear recollection though that it was positioned precisely as such in that whitepaper. It makes sense too, as that's where it fits best when comparing the iSeries, pSeries (Power), xSeries, and zSeries. Their webpage currenly however seems to make clear it isn't in any series, and I'm starting to get the impression that the eServer 325 is the only eServer product that currently isn't in any series.
It might be that IBM is developing Opteron into a series of it's own? Currently probably a bit far fetched, but we'll see.