You're gonna want the 8KHA+, for sure.  The KT266 chipset was slow, very buggy, and isn't even manufactured anymore, to the best fo my knowledge.  The 8KHA+ uses the newer, faster, and more reliable KT266A chipset.  Basically, it's the same board, but with a different chip plunked in.  Price/performance/etc. your best bet would be not to consider the older one and go for the 8KHA+ 
