Maximized Fire Seeds. First of all, fire seeds uses a d8 for damage, so there's potentially lots of variance. Maximize on a d6 based spell gives +2.5 to average damage while on a d8 based spell it gives +3.5. If you're interested in killing a single target ASAP, then Max Fire Seeds yields 160 points at level 20, compared to 120 from Max Chain Lightning. While Fire Seeds can miss, it is a touch attack so hitting is pretty easy and it can also critical.
However, Empower is much better than Maximize. First of all, it is legal to apply empower multiple times. Therefore, it's much better with lower level spells since they can be empowered many times, while Maximize only works once.
BTW, metamagic feats don't see each other, each is applied to the spell independently. So a Maximized, Empowered Fireball does 60 damage from the Maximize and another 5d6 from the Empower.