You are right, mostly button layouts were changed and the color of the lights got changed, and the MKII supports Serato/VDJ , the MKI is tractor/VDJ, Id like the option to be able to use Serato natively
Some good deals on the buy and sells here there was a pair of Yorkville 12" monitors for $200 and MKII for $225 and one guy had a pair of Parasource with stands and wires AND a Yorkville Mixer PGM8 I believe for $750...That's about $3300 worth of gear new for $750. They appeared to be all pretty clean. I resisted the temptation but I'm sure at worst case I could double my money flipping it
I have a soft spot in my heart for old skool two or three channel analog DJ mixers - the kind you'd sit between two turntables - like Stantons, etc.. I watch ebay's actual auctions for them and if the price + shipping is low ($30 ish), I'll use Gixen to put in a low bid right at the end of the auction.
When doing stuff like this, be prepared to break out the soldering iron. A lot of these are from the 1999-2007 era, and suffer from failed aluminum electrolytic capacitors.
I also usually remove the crossfader - another source of distortion - and just use the channel faders. The real beauty of these things is that since they usually run on 12 volts (or more) input voltage, they have a lot of headroom vs a controller.
When I die, my kids are going to be wondering what the heck I was doing with this stuff!! Fortunately, there is very little actual money in it.