PC60 then, which is based on 80mm fans and is in no way comparable to a case designed 6 years after its initial concept. Especially when its number of fans, and size of case are not comparable either.
PC70 - Stacker maybe, but the PC60 is a completely different class of case to the stacker, so of course it will be cooler
15 deg difference, I do not beleive that for one moment. Have you changed anything in the system, updated the bios, moved the pc out of the oven?
15 is a huge amount, usually you see 3/4 going from a PC7+ to a stacker, so maybe 7/8 TOPS and I mean TOPS in actual temperatures from the switch.
Best stats like that I have heard of, temperature sensors on a PC7+, mate claimed a 18deg drop on system temperature from his old PC7+ to a v1000+. In the PC7+ the thermal probe was on a raptor, on the v1000+ it was the top of the case so there was really no difference in temperature for most of the system.
If you could clear up the circumstances of a 15 degree drop that would be great.