At the very moment i have single channel 4gb RAM, people on forums have all been telling me to upgrade to dualchannel 8gb. my question is how much will 4 more gigs affect games like BF4, and how much will 8gb in dual channel affect games like bf4 instead of single channel 8gb
Using dual channel memory doubles the memory bandwidth, but this extra memory bandwidth isn't utilized properly, so the difference is minimal, probably un noticable. The differece between 4gb and 8gb in games probably will be noticeable.
Saying it isn't utilized properly isn't really correct. The extra bandwidth just isn't being used. This is the case when using a discrete graphics card. When using an igpu, it would help quite a bit since ram is used as vram. If you check your ram usage when gaming, you are probably using it all up so the increase in ram will benefit you either way. You already have a 4gb stick, it makes no sense why you would go to a single 8gb.