With the price of a P45 and X48 MB being about $100 difference;
-> and the price difference between the 4850 and 4870 about $100;
- -> it's beginning to look like the smart move would be P45 and 4870 over the X48 and 4850.
Except maybe for anyone using a 30" monitor.
For Crossfire set up for identical prices you could have;
X48 and 2 4850 or
P45 and 1 4870 and 1 4850
Anyone buying just one GPU now and planning to CF later could get about 15-20% more performance while waiting to get the 2nd card.