IMO drop the Pios and add Denon MC6000/MC3000
Why? Drop the Pio because the three Pio controllers does not have the regular top quality from Pioneer just the regular pricetag so you will get mid quality gear for the price of top gear. Don’t get me wrong Pio does good gear but it does not match the price!
Why add Denon MC6000/MC3000. Because it has better quality than S2/S4 IMO in terms of better joggs better knobs better faders better soundcard better chassies and you can use it together with any software that money can buy.
The s2/S4 can be used with any SW but it has a layout that is not so good with any other SW than Traktor IMO.
If you could considder ITCH also add Numark NS6 wich IMO is the only controller that is as good as the MC6000/3000.
But it is not good for traktor for the same reason as the S2/S4 it is best´for ITCH.
//DJ Hessler