I've been mulling the same, but decided against (for now)

Using Claude Code Max 20 so ROI would be maybe 2+ years.

CC gives me unlimited coding in 4-6 windows in parallel. Unsure if any model would beat (or even match) that, both in terms in quality and speed.

I wouldn't gamble on that now. With a subscription, I can change any time. With the machine, you risk that this great insane model comes out but you need 138GB and then you'll pay for both.