Not at all
If you look at how the +12V rails are allocated, you find that +12V3 is dedicated to the two PCIe power connectors.
As there are only one 8 pin (100W) and one 6 pin (75W) PCIe power connector available, only 15A (175W/12V = 14.5833A) is required from this rail.
The 25A provided is more than enough with a little extra to spare.
Combine there are 45A (540W/12V) avaliable accross the +12V rails.
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