That looks like a great setup, covering everything you say you’re looking for.
Here’s my subjective thoughts to add to the conversation…
I would add the 301 last as you’ll benefit greatly from knowledge you’ll gain from experimenting with basic modular patching before getting one. Patching within the 301 (ie adding, connecting units) requires you to conceptualise the patch in your head to a large extent, I found.
I would get a Disting MK4 (or EX) in there early - even if you don’t end up keeping it - it would be invaluable as your rack evolves because you can try out a huge range of utility modules (and Oscs, and Samplers etc) to see what adds most value.
Go for a TXo+ if you can - as it improves over the original TXo when being used as an oscillator.
Are you planning on using the O+C for envelopes? I found that was its weakness because I believe they only go to +5V and often you want to push a VCA or CV input further than that.