A couple of things.
- Agree with John that you are done with synths. You have what you need. The trick is to learn to program and play what you have, not get more at this point.
- Certainly a good mixer is needed. And if you plan to record into a computer with a DAW then a number of mixer companies have mixers with a built in audio interface and can record something like 16 tracks independently/simultaneously. Starting at the bottom of the price spectrum with Behringer. In fact you might look at their newer range of digital mixers if you want to spend some money. Excellent bang for the buck:http://www.behringer.com/EN/Category/Mixers.aspx?s=A400
- Effects: well, most of the synths you are using already have effects to shape the sound. Once recorded you might find that software effects are an effective way to go. Whatever DAW you get will come with some effects, and you buy more as needed. There are amazing things out there and they are very convenient to use "in the box".
- DAW: there are of course a number of good ones, and they share a lot of similarities. I ended up using Reaper after trying a few others. But it had what I wanted in a way the others lacked. The moral is that you have to start using something before you learn what you like and don't like, what you want and don't want. Reaper is inexpensive and versatile and a good starting place for those reasons.