Thoughts? Comments? Well the rules are pretty opaque in this one and as far as the wording goes either could be correct. Its really going to depend on your DM and whether or not he is sick and tired of you using Sudden Maximized Fireballs in every major encounter or not. If he's already mad at you then your probably SOL but otherwise you might manage to convince him to allow all Metamagic feats to cost one spell slot less then normal. Maybe another way of looking at it is; if your in a combat heavy campaign this should probably only help out one feat. Various enhanced Fireballs are already powerful enough. However if your in an RP heavy campaign then allowing everything to stack is probably better for the story as a whole - for one thing Fireball is less likely to be the obvious recipient of Arcane Thesis in such a campaign.