the dx7 has no filter and you are doing nothing but fm,
I kinda almost wish I had a tx7 because of how much room the dx takes up,
One of the solutions is getting a TG-77 (the rack version of SY-77) - in theory it has "best of both worlds", since it comes with up to four layers of FM sounds, and its operators are not only limited to sine wave, so it's possible to get waves rich in harmonics without sacrificing operators. It also comes with some samples (AWM) - not the pinnacle of realism, according to modern standards, but enough for a transient part of the sound; surprisingly, they can be also used as modulators for the FM parts (it is called "Realtime Convolution"). Last but not least, it has a filter and two FX processors. Moreover, it's SysEx implementation is well documented (in a usual Yamaha way), so it's possible to use BCR2000 to have a kind of "analog" hands-on interface for FM.
While AN1x is able to use FM, it is limited to two operators (oscillators), and it doesn't have dedicated pitch/amplitude envelopes per operator (with looping). Frankly, even though it lacks all the mentioned features, it's still a cool and relevant synth, and it can deliver interesting FM sounds.