You stated that the rack is for sequencing. Steppy only does gates/triggers... no CV/note values. How do you intend to actually sequence with it? I wouldn't depend on the MOTU for CV as you'll find it's a bit clunky going back and forth from your DAW to Eurorack just to get it to play a note. If you insist on using your DAW a MIDI to CV converter might be much more intuitive or a dedicated module like an Expert Sleeper FH2 might be a little more along your lines.
Sequencers are really a matter of use/preference... so you can go for something like an Beatstep, Eloquencer, Squarp, Toolbox, Westlicht Performer, etc. But I would definitely have some sort of hardware sequencer around... they are also great modulation tools for filters, etc.