On closer inspection it still looks like the Athlon XP Thoroughbred is the better deal while it's still around...
Athlon XP 2600+ Thoroughbred (266MHz) = 2.13GHz
Sempron 2600+ is only 1.83HGz @ 333MHz FSB
Anyway it doesn't compare in price to the 2000+ I'm looking at, even if it is faster than that!
Anyway feel free to post to this with any information, but I think for the price of the system to stay down an XP 2000+ will be going in for now - then when the Sempron goes down it could be "upgraded" later.