Damage Conversion Question/Theory Crafting idea...

Ok so I was looking at http://pathofexile.gamepedia.com/Damage_conversion.
So to use there style example tell me if this is correct...

A players weapon has 100 physical damage
They are using x2 which converts the remaining physical to cold.
and they also grab from the passive tree Avatar of Fire (50% of Physical, Cold and Lightning Damage Converted to Fire Damage,Deal no Non-Fire Damage), I assume this passive is applied after all the conversions are made so the resaulting damage would be
100 cold damage from the skill and the jewels that Avatar of Fire would convert 50% of that cold damage to 50 fire damage.

And my real question is this...
How would/when would the elemental damage(not cold/fire/lightning) increase from jewels and passives effect it all?
Is it before or after? The above example if the player had 200% elemental damage increase from the skill tree. Would it increase the 100 cold damage into 300 that the avatar of fire would then convert to 150 fire then increase the 150 fire damage to 450 fire damage? or is the elemental damage applied after avatar of fire?

I ask this cause I was thinking of making a glass cannon kind of toon with 271% elemental damage increase plus another 115% cold and 115% fire damage increase and depending on how you do the math adding avatar of fire could be really nice damage boost or really bad. I know I made an Ice Crash toon that uses Oros Sword and when I grabbed Avatar of Fire on him it did not really change my dps it only stopped me from being able to freeze mobs lol

Nah, bonuses don't double dip like that with Conversion, it's one of the reasons people are so up in arms against derived DoT double dip, it's technically against old established game rules.

Modifiers apply after conversion, but modifiers to any damage type that the damage ever was are allowed to apply. I like to think of it as "Conversion Remembers." In your example you would have:

100 phys -> 100 physcold
100 physcold -> 50 physcoldfire (the other 50 physcold is wasted because of Avatar of Fire's "Deal no non-Fire DamagE")

50 physcoldfire * (1 + 2.00) = 150 fire damage

In practical terms, if you want to use Avatar of Fire, you really really want to get 100% of your damage converted to Fire. For Cold damage, this is actually pretty simple; you just need the Cold to Fire Support and Avatar of Fire takes care of the rest.

So, for example, if your weapon has 100 physical damage, you use 2 Winter Burial, Cold to Fire, and have, like you said, 271% increased elemental, 115% cold and 115% fire:

100 * (1 + 2.71 + 1.15 + 1.15) = 601 fire damage.