Karaoke Forums

The CFX effects are the same as the DFX.  An outboard Lexicon will sound better than the built in on the Mackie just because Lexicon makes a great processor.  The MPX550 is a very nice processor - but honestly a little overkill when the MPX110 will sound just as nice.  The 550 has some better reverb patches in it, but not enough your going to be able to notice - it is better suited for pro-live music & studios.  The MPX110 isn't as programable is it's downside.  But it does have a tap sync so you can tap to the beat & have a perfect effect every song.
Nice thing is with the CFX & an outboard effects, you can blend both the internal & external together for a more custom effect.
If you go for something like the Mackie 1642VLZ (my next board) series, you are going to have a cleaner sounding board than the CFX/DFX series - these use the same mic pre-amps that were found on their 8 buss recording boards & the 56 channel touring boards.  Also more routing options especially if you want to record as well.