Personally for Wall of Fire I use Tinder, a +1 Superior Combustion IV Staff. It rarely drops in the desert from the firebrand gnoll area off of Haraja the Firedancer.
As far as looking for potency items I would assume that you would be able to find Superior Potency V as a level 12 minimum item. Recalling off of other potency items I've found Superior Potency I was minimum level 4, Superior Potency II was minimum level 6, and Superior Potency III was minimum level 8. Following these items there appears to be a pattern. I recall also seeing an item on my end reward that had 3 clicks of efficacy V, but I doubt you are worried about efficacy items.
I've gotten a couple Superior glaciation V items, but that's definatly the highest I have yet to see...Which is one reason why you certainly won't see anything but the most clueless Sorcerer wasting his one and only 7th level spell slot on the overcosted/underpowered Delayed Blast Fireball...
I've recieved a Superior Devotion VI as an end reward. Think that's +50% to healing spells lvl 1-6. It was gained from the quest in House J that you get from the NPC that's on the fallen pillar that's slightly extended into the pool near the entrance. Maybe there's an end reward on the quest for a fire based item?
The best I have for fire is a +50% to lvl's 1-5, but I also have a plethora of other clickies, items, feats, enhancements to ramp up the damage potential. :D
Hitting with a firewall 'tick' or a scortching ray for 450-490 dmg is not uncommon.
I have seen superior potency items as high as VI,
and I have a whole bunch of Superior Combustion VII items waiting for delayed blast fireball to be worth casting.
hehe check the date... this is way old.
You should be able to find a sup potency 4 pretty easily, if not, look for a sup combustion 4 item.
Again, this is a very old thread. Let it die.