As guyaguy said, an audio interface and you should be set really...
Seems to me you have plenty of equipment starting out, so my main advice would be to take the time to really know each piece you already have. Find their/your sweet spots, 'cause many times it's not about how much a piece can do (in terms of technicality), but what you can do with them (even with seemingly very limited ones). Often too many options can actually be a hindrance to creativity, at least for me personally... ie you can get lost in all the options, and sometimes just taking the time and experimenting can lead to happy accidents. And more often than not, it takes time to learn those sweet spots and really appreciate your gear. Too many buy and sell gear without having got "there" first. You not only need cash for a piece, but time.
The Rev2 doesn't support external CV, so it may not fit "together" with a Matrixbrute, for instance, in that sense...
As you have an iPad, I'd recommend some quite cheap classics like the Minimoog and the Odyssey, which can be very inspiring in terms of limitation. Not necessarily for recording, as any concept could be expanded on your other, "more capable", synths. But often "simpler" synths and setups go a long way for creativity, ideas and "blueprints".
Just food for thought!