WEll bro, you're never gonna bulk up if you're not willing to go up in BF%. You cannot help it no matter how perfect your bulking diet is. You will gain some fat do to surplus calories.
If I were you...........................I would bulk the fuck up to like 40pounds heavier than you are at which point you'll probably be freaking cuz you'll have no abs, then hit some primo and winny plus clen and t3 and in 3 months you'll be as cut as before AND BIGGER and STRONGER.
That's just what I'd do. I think it's great that you're ripped bro, but you're actually hurting your progress with this obsession about staying cut. If you want to be cut and bigger then you have to bulk.
I don't know if you use AAS or not, but if you don't then you might as well hit up something light like anavar and primo or whatever and eat just a "little" more than you do now and you should be able to put on a few pounds of nice clean muscle while maintaining your bf% close to it without getting bulked up. Probably not gonna happen without at least a little AAS though.
I am a newb to AAS, so take my opinion for what it's worth, but this seems to be the most effective method from what I"ve been reading.