depending on your needs.. but in general i'd say the X2 3800+ is better. unless you're STRICTLY video encoding/decoding ONLY.. then maybe intel is the way to go.. if you play video games, and do a lot of other stuff then the AMD will be your choice.
as for motherboards... i don't think some are more compatible then others... it all depends on your budget and your needs.. can't just say a brand in general. all the brands make both good and bad mobos..
"Is virtue a thing remote? I wish to be virtuous, and lo! Virtue is at hand." -Confucius