I'm not sure if it has been discussed on the forum (I might have even brought it up before but just can't remember), but Fluval has released their FX6 to replace the FX5. It doesn't appear to have major changes. The FX6 comes with media, has been lock down nuts, couple cleaning reminder dials, but basically is the same thing.
At least initially the FX6 sounds like it is going to be significantly more expensive. $50-$60ish.
FX5's should start not being available from most retailers in the 4 to 6 month time frame in case you wanted to go the cheaper FX5 route.
Just an FYI to the forum.