I’d suggest grabbing an Arturia Keystep or Beatstep Pro for sequencing and save your Space for more modulation sources. For about $120 you get a solid keyboard controller with a built in arpeggiator, sequencer and you can switch MIDI channels while the sequencer keeps playing and play live over another channel. Great performance tool. You could also drop in a Mutant Brain and use any MIDI device for control like a Novation Circuit, MPC or Digtakt. The Mutant Brain is completely customizable giving you plenty of cv/gate/trigger and even clock division options for output. Using an external sequencer is going to result in far more control over compositions at a much lower cost. If you want a more randomized or more generative composition, try a shift register and quantizer combo along with a keystep to enter root notes that the system can then transpose or riff off of.
As far as stereo goes, I think it’s worth it if you can find the right mixer module that fits your system without taking up a lot of space. The intellijel Mixup is a great little stereo mixer with plenty of inputs and stereo output in 6 hp.
Also, I tell this to everyone: get an Expert Sleepers Disting Mk 4. It’s an amazing module in a very small package. It’s probably the best wav player/sampler/Swiss army knife for the price and keeps getting better and better every update(which is very regularly).