What I discovered with my h'ware was that NB cooling effects directly CPU temps. Bare in mind my rig is a museum piece now (and it pump s MUCH more than 10 watts through NB)
Peeps tend to forget that MoBos are very good heat conductors (lotsa copper there) and if you i.e. supercool your NB (even if it does not need it that much) nearby elements temps are going to be effected in positive way (lower temps). That's why I am going to slap 130 watter TEC on my NB soon