The Xserve now accepts 4GB memory modules and can recognize up to 24GB of RAM in the single-processor model, and 48GB in the dual-processor system. Both machines can also now be configured with 2TB drives (up from 1TB), expanding the official capacities up to 8TB for the Mac Pro, and 6TB for the Xserve.
None of these upgrades come cheap, of course. The 3.33GHz Xeon adds $1,200 to the default 2.66GHz unit, and $800 to the 2.93GHz chip. Meanwhile, choosing 24GB of RAM increases the price by $2850, 48GB costs $5,850, and Apple is charging $550 for each 2TB HDD. All of these options are available today, but they could add two to four business days to the processing time.