Which cdjs should I go for ?

Hi there, i am looking to upgrade my equipment, currently using a mixtrack pro almost 2 years old has served well but really wanting to get a hold of some cdjs and a mixer, which to get is the problem. NOTE I have researched and got most of the information and narrowed it down slightly however just wanted to hear some opinions.

Initially i was VERY keen on the idea that you can just plug in a usb to some of the cdjs and play off that for obvious reasons, no piles of cds and bit of an effort putting music on them. I still am keen although I didnt realise that only some cdjs have the usb link function allowing access to one usb from both players making life 10x easier. A clear waveform was also a big part of me but have realised thats not so importnat if i want learn to mix more proffesionaly. the cdj 900 is the cheapest player to support link function im sure and for a second hand pair its at least a grand, without mixer. So basically is there any opinions to support buying the cheaper cdjs, as the idea of having two usbs, with basically the same music on them just so i can play from them on both players ( i know that sounds stupid from me) I know cds arent that bad but they just sound like more hassle compared to usbs. And i know that if i want the better stuff i have to shell out but i just want the best form what money i have – obviously open to suggestions, Thanks! (ps know theres lots of forums on this subject but looking for specifics)