I have read places were the best option is the aqua clear, but then i compare the gallon per hour they run. Ac70 is 300 and emperor is 400..its a big differnce i believe. Would this make a differnce to you in picking one?
I'd get a pair of AC70s. More flexible media options and redundancy in case one fails (pretty reliable...had an old smaller model from the 80s and it still ran a few years ago).
Emperors are nice but noisy.