Add another 8GB stick — it's cheaper and usually works.

Yes, adding a single matching 8GB stick is almost always cheaper than buying a new 16GB kit. A new 16GB (2x8GB) kit usually costs $25-35, while a single 8GB DDR4 stick runs around $12-18. So you save roughly half.

The real question is compatibility. If your current stick is the same speed (e.g., 3200MHz) and same CL timing, just plug it in and go. Mixing brands or slight timing mismatches usually works fine on modern boards because the system downclocks to the slowest stick. Worst case: it doesn’t POST and you return it.

You lose literally nothing by trying the cheap route. Only buy a full kit if you’re building from scratch or want guaranteed dual-channel matching for overclocking. For normal use, the single stick is the smart move.

Don’t overthink matching pairs for a basic upgrade.