I had hoped you would have posted temps by now. This has the potential to get confusing so i will attempt to nip that in the bud.
Gpu temps up to 85 degrees are fine as far as im concerned. Any thing above that without over clocking the GPU is a cause to worry.
A quick PSU lesson. The PSU supplies the power but does not push the power to the parts , rather the parts pull power from the PSU.
If the PSU is inadequate then the parts struggle to pull the required power, much like a strong man pulling a large truck or aeroplane they get heated with the huge effort evolved with trying to pull a load that is unrealistic.
This will have the potential to make the part(GPU in this case) overheat and/or make the PSU over heat.
If this goes on for long enough or the differ ential is large enough either the PSU will die or the part will die or if you are really unlucky you will get a full system melt down and the whole system could get fried.
With a modern PSU the last possibility is a faint one with much better over currant protection these days but is still a possibility none the less.