I don't think brains can evolve to be much larger without major redesign of the female pelvic reason. in fact, the reason childbirth is so much harder for human women than most other animal species is that big ol' brain. (and my daughter's head didn't change shape, so I know what I'm talking about.) in fact, human babies are less able to survive than most other species immediately after birth because their brains have to keep developing after birth in order to allow their heads to still be small enough to pass through the birth canal.
I also don't think that complex=better; if that were true, wouldn't there be way fewer bacteria on Earth? complex may be better for certain evolutionary niches, but it isn't for others.
"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"
"You can't erase icing."
"I can't believe it doesn't work! I found it on the internet, man!"