Hello Cowby!
Without being any expert on any of these Yamaha stuff, this is what I think;
1. PSR-2000 and QY700 are quite similar in the quality of the sounds. If there are any differenses in quality, they are small. The big step is to your other equipment.
PSR is clearly better to use as an realtime arranger (AC) and the QY has got a terriffic sequencer clearly above the PSR.
2. The Triton as a controller and the QY as AC and soundsource is no problem. But I don�t think it is possible to use the Roland for the pattern sounds. But it�s OK for solo sounds.
Regards, Michael