the penguins and emperors are not bad though man. i run the emp 280 and 400 on my tank right now.
i would hesitate to replace all of your filters if they are functioning properly, but if you ever need to the aquaclears are definately my preferred filter.
this is not anything other than my opinion or observation, but it seems to me that the longer people are in the hobby, the more they start to lean towards the aquaclears over the other types of HOB filters. the cheap and easy maintenance seems to be the real kicker for the old-timers i suppose....
i know that I personally think that they are better for the money, and you cant beat the sponges that never die!
M