yeah this is all about greed, bios are the only reasion, chipset has NO EFFECT on this, there are am2 boards with sis chipsets that came out long b4 the am2 socket came out(well use to be, havent seen any for a while but i have seen them and used them)
this isnt like am2 vs am2+, alot of am2 boards lacked enought room in their EEPROM's(bios chips) to accept the needed code to support k10, Really any am2 board could take a k10 IF u replaced the bios chip with one that was large enought containing the am2+ bios the board would support those chips.
Also talking about the 125 and 140watt cpu's and some am2+ boards, this was due to volt chips used, alot of boards blew out on 9850's at stock clocks due to power draw excceding what the boards chips could maintain, I have seen 790fx msi, asus, gigabyte and other brands burn out.
weird one was the biostar ta770's a cheap board thats managed to support the 9850be without blowing dispite being a cheapo board(but a great one for clockers)
board makers should have thought ahead and used better fets but they didnt, so well, rev2 boards had to come out to support 125 and 140watt chips.
cant wait to see the new chips, From what I understand biostar plans to offer bios updates to support new 45nm core chips, so they are a good bet if you want a kickass overclocking board, the ta790gx3 is a pretty sweet board