If it’s purely for experimentation then why not the DGX Spark/GB10? It’s up about 10% from release RRP which is quite good (you might argue it was overpriced then, but prosumer and workstation GPU prices are up 100%). 4TB NVMe is not cheap these days - it’d cost at least $500 for a stick - and you get 128GB at a similar bandwidth to an M5 Pro.

Nevermind that Apple still insists on providing base systems with only 512GB of non-upgradable SSD. The equivalent spec mini (4TB/64/10G) is almost $5k for half the VRAM. Not as good a CPU compared to the M5/6 but you also get 20 cores and full CUDA.