How strong are the Marine Admirals? Since the Navy mainly determines power through bounty.  They seem strong but Whitebeard was able to fight all three admirals at one.  Also the Commanders of Whitebeard were on par with the Admirals. So how strong are the Admirals?  How much bounty would they get if they got one?
The Navy actually doesn't determine bounty based entirely on power, they also base it on how badly they want the particular guy caught.

Considering how DonFlamingo's bounty was 340 million beli, and he was a pretty big deal,  It appears that the marines start leveling out the bounties around the 300-400 million range.

That taken into account, If the admirals were pirates, their bounties would likely be in the 300 million range.

As far as power goes (and power is not that quantifiable in one piece), they're all in the top league, and so far, the only character who was formally introduced who can be said to have a very clear advantage over the admirals is Whitebeard, and he's dead.  

the Other Yonko are very likely to be stronger than any particular admiral, but that's not necessarily a concrete rule, and we yet to have a good measure of their power.