I found a socket 754 Sempron processor at overclockers.co.uk which could show that the higher speed processors in the new range are going 754 in there socket.
linky
http://www.overclockers.co.uk/acatalog/AMD_Sempron.html
Right at the bottom of the above link.
Edit: is the size of the cache that important??? should I be more looking into 512 cache size over 256?