Its not also just a matter of power, but how _long_ can it support it. ie its heatsinking capabilities.
Ie go boosting in the hills for half an hour on a warm day and I'll guarrantee you'll burn your hand on it, even with say 150rwkw. However have 200rwkw and have a 5 second fang in a cold night and it wouldnt be has hot as the previous example.
Basically for heatsinking purposes, all stock intercoolers are built to a budget. ie quite poor.