miniKORG 700s from Korg Collection 3 is amazing. Can do lot of very different sounds from smooth to MS-20 like and also good for sound effects. Distinct sound, definitely not just another subtractive synth.
I am not impressed by Prophecy. While synth is quite complex its not reflected in final result - sound is not distinct. There is no wow effect like in M1. Do not buy separate.
Triton Extreme is just a free update, if you own previous one.
If you own Korg collection 2 (without Triton) upgrade with sale discount for $150 is very good deal - you will get Triton, miniKORG and Prophecy. Triton alone is $250.