This 2TB NVMe SSD is a great Steam Deck upgrade for £155
Corsair's MP600 Core Mini SSD works well in the ROG Ally and Legion Go too.
Corsair's MP600 Core Mini SSD is a solid option for upgrading a PC handheld - devices like the Steam Deck, ROG Ally and Legion Go and so on. It's a PCIe 4.0 NVMe SSD, so it offers slightly faster speeds on the latter two devices than on the Steam Deck, but it's compatible with all three major options. It originally retailed at £230 for the 2TB model, but now it's at a much more reasonable price: £155.
In terms of the speeds and feeds, the MP600 Core Mini is faster than the previous 2230-sized Corsair SSD, the MP600 Mini. It's got rated sequential speeds of 5000MB/s reads and 3800MB/s writes, while random speeds are also quite competitive at 550K IOPS and 900K IOPS for reads and writes respectively.
The MP600 Core Mini is based around QLC NAND with a DRAM-less design, which is fairly typical for these kinds of 22x30mm sized SSDs in the 2TB size. There are some TLC designs on the market, which tend to offer better performance and longevity, but not many 2TB options. This drive comes with a five-year warranty as well, which is pretty neat.
Overall, a solid option for upgrading your Steam Deck or whatnot, so do consider it!