Okay. I'm going to post the multipliers below.
We know the Tsuna's choice arc X-Burner is 176.22 megatons. Byakuran was able to casually stop an attack with the strength of the X-Burner, and said that he hadn't even used 10% of his power. While YungMazi makes a good point about why he is not a particular fan of this multiplier, I believe it to be usable purely because Byakuran did casually halt a 176.22 megaton attack with zero damage. He literally clapped his hands. This results in a ten times multiplier, taking us to 1762.2 megatons, or 1.762.2 gigatons.
Next up, we have Enma. He was able to casually stomp Tsuna and all his guardians at one seventh of his full power. The reason why this multiplier can be used, outside of multiple reliable statements, is literally because the plot of the arc, in part, revolves around such. Tsuna has to save his friend, but must become strong enough to do so. And the two only fight because Enma is drunk on his newfound power, which is blatantly stated to be seven times stronger than when he had initially received his ring. This increase in strength actually applies to all the Shimon rings. So, taking our 1.7622 gigatons times seven gives us 12.3354 gigatons.
Daemon Spade states that he only has access to 10% of his power while in Julie's body. Yamamoto should be weaker than Tsuna and Enma, but not by terribly much. To be safe, we can assume Yamamoto to be the aforementioned 1.7622 gigatons. Which would make Daemon within Mukuro's body 17.622 gigatons.
I don't believe the last arc gave us any multipliers aside from Kawahira stating that his flame output is ten times stronger than Tsuna, granting him an at least 176.22 gigatons for his AP.
This is the chain that I find to work best, using reliable statements. Is there anything that anyone disagrees with?