I lived that era, and don't miss the DX7 at all. Yes, when it came out it was revolutionary and if you wanted to produce very thin sounds, (some) credible organs, really nice electric pianos, punching basses, and metallic sounding instruments that one was the keyboard to use, no doubt, but the drawback was that almost everything else would sound terrible, I mean really awful. Additive synth is great only if done well, and the first DX synthesizer were a lot limited in some fields; if you tried to make a track only using a DX7 it would be a compromise wrapped around other compromises. For starters, operators could generate only sine waves, and every other waveform had to be emulated by frequency modulating an operator by another synced operator; that could be used to make some really interesting effects and sounds, but no way one could produce for example believable strings; they were just terrible. Also it had no filters, that is, no VCF/DCF/whatever, so no way to produce credible sweeps or warm pads that would have been trivial to produce with a 10 years older keyboard. DX7 has been revolutionary for sure, but had its share of limitations, and (plugins aside, of course) rather than spending money on a vintage DX7, I'd get a smaller and much cheaper FM expander to be driven together in unison with a traditional analog sounding one; the 1st one for the aggressive attack, the 2nd one for more warmth. As for additive synth, I deeply regret having sold my Kawai K5000 years ago; that was really a beast. Heck, That applies pretty much to all my old gear, but sometimes one is forced to, only to regret much later.