I have a 2017 iMac and a 2017 MacBook, but I also have an old 2009 13" 2.26 GHz Core 2 Duo MacBookPro5,5 lying around here. I don't want to invest too much into it, but I find even with light usage the 4 GB it currently has is limiting. Easily hits the swap, and even with the SSD I have in it, I get the spinning beachball every so often. I could simply upgrade it to 8 GB, which would be ideal, but given that it's really just a guest machine now, I thought it could actually make sense to forego the dual-channel speedup for RAM, and just run it with 6 GB. What do you think? Note that I eventually want to hack it to run High Sierra. Apparently, High Sierra runs perfectly on this model, which isn't a huge surprise, since High Sierra supports a later white MacBook that has the exact same internal specs. Damn you Apple for leaving this machine out of the Sierra/High Sierra love! Mind you, if I really do just leave it as a guest machine, it may even be OK with 4 GB, assuming they just run Word plus Safari with a few tabs open and nothing else. --- Post Merged, Jul 8, 2017 --- Hmm... Strange. I just checked OWC, and their memory upgrade is $31.99 + $4.45 shipping for 1 x 4 GB, and $59.99 + $2.67 shipping for 2 x 4 GB. So that means $36.44 for 4 GB and $62.66 for 8 GB. So, the difference in price is only $26.22.