I've heard mostly great things about the DPO, as well as the Z2040. I'd consider adding a dedicated AD or ADSR, because Maths does so many other things that you might not want to have it as your only EG. You should consider losing the EON and get the Expert Sleepers Disting MK3 -- it's not much more cost-wise and perfect for a small system because it has so many functions (everything the EON does and much more). You can experiment with it to see what you tend to use most which would help determine future purchases, even if you decide not to keep it. From hanging out over at Muffwiggler, the consensus seems to be that you "can never have enough VCAs"... of course it all depends on what you're trying to do, but adding another 'flavor' of VCA might be advisable. The ModDemix would be a good option, plus it can be used as a mixer within your system, which would be useful. Something like Mutable Instruments' Links might also be useful. Finally, I'd add Clouds (fantastic- I have one), or something like the Echophon or Erbe-Verb since any of those would be valuable to have for what you're trying to do.
Disclaimer: I'm not new to music or electronic music, but am new to modular. Since purchasing my "gateway" to the modular universe (Moog's Mother 32) I've spent nearly 2 months buying, selling, trading (and blowing up my budget, originally 120hp, now 208hp... gaah) and finally think I have a system that should hold up for awhile. It kinda has to since I can't (shouldn't) afford to do anything but sell or trade out at this point. Also, if you've not been over to Muffwiggler, it's highly advisable as it is a treasure trove of information and discussion. AWESOME community. Just for kicks, here's what I ended up with: 