FM is all the rage these days, primarily because of the work done across the board on improving the UI and programming experience. Its become less impenetrable and as such opens up the impressive synthesis engine.
Native Instruments FM8, the version after FM7 has also pushed the envelope, with a 6 Operator FM engine, the FM Matrix, Morphing plus a deep level of editing for LFOs Envelopes and Effects too.
All this would usually set you back around £129, or be part of the NI Komplete bundle, but Plug-in Boutique have a Summer offer running where its a mere £12.
So even if you just want to flip the 960 included presets or load up some original DX7, DX7II and DX200 SYSEX files, its a bargain.
Matths gives it a workout
From recent Brighton gig
And the George Formby grill