Should I buy a 2x16GB RAM kit instead of adding another 2x8GB kit?

Just buy the 2x16GB kit. Mixing two sets of RAM—even identical model numbers—can cause instability, especially with XMP/DOCP. The memory controller runs all four sticks at the slowest pair’s speed, often forcing a fallback to JEDEC speeds like 2133 or 2400 MT/s. A new 2x16GB kit guarantees compatibility, full dual-channel, and leaves two slots open for future 64GB. Selling your old 2x8GB for $25-30 makes it cheaper.