In the game I play in on Sundays I play a Sorcerer/Shugenja. It seems that I'm always looking ahead and planning what spells I'm gonna learn at each new level since my spell lists are so small. I'll have it all planned out then I'll read some more and change my mind or I will notice what the other folks in the group are constantly doing and switch to a spell that better fits the group. It seems like I spend a lot of time doing this (I know part of it is my own neurosis).
I started playing D&D as a fighter, usually mixed with other classes, but a core fighter nonetheless. I love the simplicity of it. You got your feats, which you know inside and out and you got your weapon to do all kinds of sick damage. Easy-peesy.
Then there's the spell caster. Honestly, wizard is my new favorite class. I completely understand where you are coming from, Chris because I am the same way. I think I drive my fellow gamers and DM crazy with it all. I know my spells (durations, variables, DCs, the works) and I usually have it figured out before my turn. But then someone goes and does something crazy, then I have to figure out an appropriate reaction/spell to it. It's frustrating, but crazy and definitely fun.
Stick with what works. It sounds like your system works great just remember it's a game and have fun with it. Don't worry about what the other characters are up to. Something I had to learn the hard way: While it's great to build a character the group benefits from, remember it's a role-playing game. Choose spells that suit the character first, then worry about how the party will benefit. I think it's more fun that way.