That amount should be plenty.
Also, unless you have a specific use for Steppy, you might want to replace it with a 4Robots (1U Intellijel friendly) version of Ornaments & Crimes. It's a multi-utility module that includes a quantizer, basic sequencer(with CV, gates or envelopes), and a lot of other nice features that you can use with yoru system. You might need to ditch the USB 1U... but that's not a big sacrifice. It's a bit more than a standard O&C. But I love mine. The sequencer is basic... BUT it'll be great for those times when you don't want to mess around with your computer and just jam out on your synths. Or if you want a sequence going internally that responds to... your logic module! :)
The 4Robots version can also scale beyond +5 volts to I think around 8volts... giving your envelopes some more bite.
https://www.plum-audio.com/product-page/1uo-c-4robots