Another motivational factor in favor of trying to stay leaner...you will tend to notice smaller increases in lean tissue. The higher your bodyfat, the less obvious any small increases in lean tissue will be. Ideal for slower gainers.
I'd echo Bbiceps recommendation to try higher rep training for awhile, like 12+. For everything. Have you run high volume protocols at all before? If you really hate the idea of not doing any lower rep stuff, Layne Nortons PHAT is a great middle ground giving you the best of both worlds. Otherwise fuk it, skip the low rep stuff completely. If you've been doing low rep stuff for awhile you will likely see a really good initial response to going exclusively high-rep. But you need to be able to enjoy doing it.
Are you also doing lots of different exercises? Like, not just bench and DB flyes for chest, for example?
Anyway....Mike Israetel has arguably some of the best material on volume training. If you're interested in going the volume route, I'd highly recommend watching his stuff, but this video should give you a basic introduction to his core concepts: