Add two more 8GB sticks.

Yes, add two more 8GB sticks if you can get the same or very similar speed and timings. It’s cheaper, performance is nearly identical, and you avoid wasting the RAM you already own.

The only reason to replace instead is if your motherboard only has two DIMM slots (rare these days) or if you plan to eventually go to 64GB. For 32GB, adding is the smarter move. Just match your current kit as closely as possible—same brand and model if you can.

If you can’t find an exact match, buying a new 2x16GB kit and selling your old sticks is a clean alternative. But that’s more effort and money for no real gain today.

Your wallet will thank you. Your PC won’t notice the difference.