I've got 2 4TB HDD's full of music and I want to put them in a NAS with another couple of 4TB drives. But you're right about the SSD's. If I can afford it I might get that 2TB, I had no idea NVME's had come down so much. How do those WD Blue's compare to the Samsung and Intel NVME's?
Intel 660p is brand overpriced QLC Flash drive at the price of TLC.
QLC is race to the bottom crap tech with worser than HDD sequential write speed after cache filling.
Yes, SSD can be slower than HDD!
Hence instead of being clearly more expensive than SN550, Intels should be cheaper.
Also Samsung's SSDs have basically been brand overpriced for years. Basically this way:
QLC SATA drive at price of TLC SATA, TLC SATA drive at price of TLC NVMes, TLC PCIe v3 at price of PCIe v4 drive...
Though Samsung's latest NVMe, PCIe v4 980 Pro is finally competitively priced even without specially high discounts.
But price jumps in general quite a lot when going to PCIe v4.
Phison E16 based ~5GB/s drives are that starting price:
https://www.overclockers.co.uk/patriot-viper-vpn4100-gen4-2tb-ssd-vp4100-2tbm28h-hd-017-pa.html
And newer full PCIe v4 speed controller drives are basically £100 more.
As for actual performance in real use, most games are limited by processing speed in loading times and usually there's little difference even between SATA and NVMe.
TechPowerUp has loading times of half dozen games in their drive reviews.
Though in not processing limited games NVMes can pull quite a lead to SATA SSDs.
But after that differences between NVMes get smaller in real world time:
https://www.realhardwarereviews.com/silicon-power-us70-1tb-review/11/
Firecuda 520 and that US70 are Phison E16 based.
Crucial P1 and UD70 are QLC drives, with the latter using same Phison E12 controller as in TLC Flash using Barracuda 510 and P34A80.