Update: According to one reseller, the channel from Ingram Micro is empty of PowerMacs, and on backorder....
...however, current Ingram inventory apparently shows 300+ Dual 1GHz machines (all localized in one warehouse), 900+ 800MHz, and no 933MHz machines available (with no supply for the past month).
An upgrade to the PowerMac line has been expected for the past few weeks, with initial expectations falling on MWNY, and most recent rumors suggesting dates of Aug 5th and Aug 13th... with one unverified submission that hints that it may be as early as tommorrow (Aug 1)