From a quick google search a DGX spark seems to decode Llama 3.1 70B (FP8) at 2 tokens per second. I would expect the performance on a 768B parameter model spread across 4 to be significantly lower even though its a mixture of experts.

For real work anything below 60 tokens per second is essentially unusable. That's not taking into account the prompt filling, Llama 3.1. 70b on DGX spark runs at about 800 tps running at that speed prompt filling a 512k context takes like 11 minutes.