This may sound like a bad idea but.....have you actually tried the morgan core in the board? It would seem very possible to me that it would work ok even though it isn't "officially" supported. At most, you would be losing out on the SSE instructions that the morgan core contains. On some games it makes a difference but on most, I would doubt it. It should still recognize the chip as a 1.3 duron or a processor running at 1.3 ghz. Considering your options, you might as well try it and see what happens. I don't see that it would hurt anything. If it doesn't work, you can go back to the 850 for now and check on a different board a bit later.
jc