Reply to Older DJM any good?

So I've been waiting for a deal to come around on a Denon X1600 or X1700 or an Ecler, but I've been a bit slow at purchasing and missing out on them

I'd like to keep myself entertained though for the time being. I know people ragged on the DJM600 quite a bit for really poor sound quality. How were the other DJMs? Considering picking up a DJM400 for 150-200, but since it's not a 4 channel mixer, it doesn't seem to have that many reviews. I'm the typical EDM house/trance (bash on me all you want) mixer with A->B mixing so I only need 2 channels in the mean time anyways until my mixing skills get better.

tl;dr: DJM400/older DJMs vs the newer DJMs. Worth the huge increase in price?