if you specifically want an adsr - get a doepfer one - they are inexpensive and will do the job perfectly well
otherwise the quadrax seems like a good deal - envelopes and lfos - which you also have in maths (but this is a good thing)
I'd get a matrix mixer next to experiment with combining different modulation sources (and some stackcables so you can use the original modulation source too)
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities