Start with the ES8 and think about what is gonna go into each one of the 4 inputs you have then work backwards from there. Think about how many headers you have in your case and make sure you don't go over 80% of your total power and then try to cram in as much as you can if you are one planning on just having 168hp. Most people on here will advise you to get a larger case, the consensus seems to be around 208hp. You can do a lot with 208hp!
You could easily build two really good voices with effects in a 168hp though. If you get the ml2 you can use Ableton Link and do drums in Ableton and this will play in time with your modular. You have 8 outs in your ES8 and you can send a lot of modulation like lfo's and envelopes out from Ableton and plug them into your modules to modulate the crap out of your cv inputs. You'll love that.