Siriothrax has an older meaning than that. we associate Sirius with the dog star because that was the god Sirius's animal symbol in greek mythology. That god's name goes back further to mean "the scorcher" or glowing, relating to being the brightest star in the sky. Technically, his name is most connected to Lucifer, in both stars and Lightbringer/glowing titles. But I'm seeing similarities in all the dragons' names. perhaps they were created to fulfill Lucifer's original purpose when he fell, or in case he did fall?

mister would take up the coin because cats are the embodiment of free will, so compatible on that end. Also, cats are selfish and take things they don't want/need anyway(I miss not having to sneak my hair ties back), so no refusing an actual gain. he would immediately use it to be able to communicate with Dresden/other slaves in a lazy fashion, like telepathy. Dresden can't pretend he doesn't realize mister wants out now... Also, cats now replace the churches holding facilities, as they are collectively too lazy to take over the world, have cultures worship them as gods so the demands wouldn't drive humans insane, and the demons have no control at all in the situation. All in all, send them to an Egyptian cat worshiping temple and nothing changes in the world with all coins in relatively harmless use.

he said the results of ONE case are running around commonly throughout the series. so one instance of soulfire. that would rule out Drakul as we just saw him for the first time, and no one said he specifically was getting more active, jus the supernatural realm.

 that would make the case for the white court stronger, but I don't think that is the case either. one case to create an entire species, who recreates. I see them more as a chemical reaction than recreation. a chemical can have a reaction chain, which can be stopped, ie, child falls in love. recreation requires two, and both contribute to the outcome. with the court, all that matters is that one parent is vampire. If it is not the case, I would like to present my own wag. Marva is the case. some theories point at marva being Morgana.
 Many theories say the merlin the most parralels with harry, so he might have had soulfire. some stories of morgana said she was his lover. perhaps merlin resurected her with soulfire, and saw himself do something so terrible, or he ruined a grace he was holding, so he locked himself up on demonreach. Morgana as Marva and the necromancy incident would also fit the specifications jim has. she has appeared in several books, including BattleGround, and was mentioned as active in others. If merlin locked himself up afterwards, he may still not be the British prisoner, as said by Jim. he would undoubtedly consider himself as severely evil, even if he wasn't, and lock himself far away from the entrance anyways. perhaps the most contained area possible. that would also explain how merlin is extremely relevant to the plot, and that's why jim never goes into detail about it, ie the story of the war for humanities memory, which is not relevant, so he can diverge at will.

perhaps he comes back later in the books to undo the spell that created marva. that could also explain marvas white council level abilities. plenty of black court could have had an opportunity to sneak attack and turn white council members. yet her abilities were seen as unheard of by harries allies when he took down her scourge. that could be explained as the act being more real, thus allowing her abilities other Blambires can. Even the wizards they took in battlegrounds were not feared for what they could do as turned, just that they were turned. another wag i have is that blampires have inate talant, like all humans, but it is extremely toned down, since magic is the manipulation of the forces of life/creation. therefore, a Blampire could only have wizard abilities if soulfire countered that in their creation. perhaps in use by a starborn was also a requirement.
 I think we could solve this case easily if we came up with a list of those that have or had soulfire, and known or speculated interests/attachments/allies/connections/events.