So I built a computer last year, and decided on 8GB of ram since I thought it would be enough. However, from playing modded minecraft and hosting a server I see it's definitely not enough, so I want to upgrade to 16GB. The ram I have is a 2x 4GB kit, so to upgrade it to 16GB can I just add another 8GB (or 2x 4GB) or do I have to replace it for a 2x8GB kit? My motherboard is a Z170A if that matters.