AFAIK, both have a 24 pin adapter, and there really should be no issue using the adapter. But as long as you find a decent PSU that has 22-26 A on the 12 volt rail, you should be fine... that's up to you.
The main reason I recommend the P180 is because the PSU is kept in the bottom of the case in a seperate compartment. A friend of mine just bought one a few months ago and just by using the case, he noticed a 7-10 °F drop in CPU and case temps. If nothing else, you'll need the additional cooling with a processor like that.
EDIT: And if you're avoiding a case because of the door... WHY? How many times do you open the door? Is it really going to be that annoying?