The only problem with those last two PrCs is that we're planar travelling for an epic campaign and I'm not sure how well those spell pools will work. Also, I believe that the planar structure in the Manual of the Planes and the ELH is different from that offered in the realms, is it not? Our homeplace is Greyhawk. If my DM will allow it, though, that would be worth looking into those.
The spellpool will allow me to share spells put in by other sorcerers/mages and in return, I have to put some in of an equivalent level, correct? I.E. I don't have Stone to Flesh, but I need it. So I "borrow" it from the spellpool. At some point, I have to cast another spell of equivalent or higher level back into the spellpool to repay my "loan." That's how it works, right?