"so if you are also worried about CPU upgradability, take P4"
LOL, ever time Intel releases an upgrade for the stupid P4, you need to get a new motherboard. It's not like they decided to keep Socket423 from the original P4 Willamette. Hell, if they go for dual channel DDR, you never know, they might up the FSB to 166 to match it with dual PC-2700 DDR...i'm probably wrong, but knowing Intel, they change sockets/slots much more often than AMD...and no, SocketA isn't numbered yet, we don't know until we see what happens with the Hammer. It may be kept as a low cost solution to 32-bit platforms, as well as seeing advancement beyond the Barton.
"When there's a will, there's a way."