this would be one of best chips for your application:http://www.cpu-world.com/CPUs/...obil...D2400FJQ4C.html
Athlon XP Mobile 2400+, 266mhz FSB (well, 133mhz actually, using 266mhz RAM - there is no such thing as 266mzh FSB), 1.8ghz, 512kb L2 cache, and 35W heat. It even supports PowerNow! that could help reduce heat issues further when its idling.
next choice down is http://www.cpu-world.com/CPUs/...obil...S2100GXS4C.html
AXP-M 2100+ at 25W heat
next choice up ishttp://www.cpu-world.com/CPUs/...obil...H2500FQQ4C.html
AXP-M 2500+ at 45W heat
two things to look for, make sure its the barton core, and make sure is between 1.25 and 1.45V for Vcore. Some mobiles ahve 1.65+ for Vcore, and they have over 70W heat.
one thing i can't seem to verify is full CPU supported list for the Ali chipset. its a dead chipset, so finding if it supports the AXP-Mobile series is a tough thing.