An nvme drive bottlenecked by a CPU ??
No that's an impossibility.
The 960 evo is faster , whether you would actually notice any difference is debatable in all honesty.
You'll obviously use the secondary as a scratch/storage drive ??
For me personally for an extra $50 the answer is no
That $50 would put that secondary drive upto a 3tb or a sata based ssd upto a 480/500gb+ model.