I just ordered the base model 8-core Pro with 2GB RAM. I'm going to upgrade the RAM myself. Do I need to stay in powers of 2? (2,4,8,16 GB, etc.) For example, if I ordered a pair of 4GB modules, that would give me 10GB total in 3 slots, assuming it comes with a single 2GB module. Is that not advisable? Do you need to keep an even number of slots filled? 10GB in 3 slots would still be faster than 8GB in two slots right? Or does it come installed with 2 1GB modules, and thus ordering a another pair would keep an even number of slots filled?