AC70 = AC300 doesn't it? If so, that's what I use on my 30 gallon longs, seems to do a good job.
As far as the psittacus, I've never had them before, so my help there is limited. But I've read a lot about them lately. I got the interest when I donated some cichlids to the Newport Aquarium in the Cincinnati area (actually in Newport Kentucky across the Ohio River from where the Reds and Bungles play). The guy that runs the Amazonian display (where my cichlids are going) showed me two new adult psittacus swimming around in there. He seemed excited to have them, and I don't blame him, they look stunning.
They might be ok until December, but I wouldn't add Severums until the 125 is established. They would crowd the 29 I think.