Hello,
Not sure about what you mean with signature, i think that this is a very broad term in order to define what you like or does not like, however let me tell you that just last week i got my new RA1570 integrated amp, i have it plugged to B&W CM1 speaker and 1 ASW610 sub, the sound is just amazing, specially at high volumes, be aware that 1570 has plenty options for input and 120wpc more than enough for running your 683, integrated DAC, Bluetooth, PC USB connectin so you might be able to get rid off some of your old stuff.
Probably i´m wrong but i do not think that you could compare pioneer with Rotel, personally speaking you are comparing a normal sport car with a ferrari, for sure there are more epxensive equipment out there that would be better than Rotel however the cost factor is also something important to consider.
Hope this helps!