a bit about processors
First off, just so you know, it is an utter falacy to compare two different processors based on Mhz. A dual Xeon machine would be very fast, mostly because Xeons have a lot of cache, and there are two of them. Following Apple's recent trends and the fact that the 970 is designed to be used in a multiprocessor configuration, I think any powermac based on them will be dual. Given the 970's amount of bandwidth and the dual floating, fixed point, and vector units, I think that even 6 months from now a dual 1.8 Ghz machine would still rival if not beat the latest Intel or AMD powered machines.