With epic money you could even afford charged staffs. I mean how many combats do you have per session and how many sessions do campaigns last? Not many. 50 charges is a lot. Basically get any spell that you want to be able to use at any time or something you want to be able to spam. If it is something you want to cast every day and only once or a couple times per day, then put it on your spell list instead. Since staffs use your caster level and charisma it's basically like having more spells known, except as noted. So yeah, go pick your new spells known.