Buy the dual-channel kit now.

Don’t buy a single stick for “future expansion.” DDR5 is weird: each stick already has two internal channels, but running just one stick still halves the memory bandwidth. You lose about 30-40% performance in games and memory-sensitive tasks compared to a matched pair.

If you think you’ll need 64GB later, buy a 2x16GB kit now, then sell it and swap to 2x32GB when the time comes. Mixing a single stick later is a gamble—DDR5 is finicky about memory training, and you may end up with lower speeds or instability. The resale value of a used kit is decent, and you get full performance now.

Future you will not regret having dual-channel today.