I'm not a great bencher, but I'll add my two cents worth. If you've reached a sticking point in flat bench, spend some time improving your decline and incline benches. It's a bit harder to cheat in those movements and will strengthen delts and tris in a different manner. Also, you might be pleasantly surprised. I'm actually around 10 kg stronger in decline than my all-time flat bench 1max rep of 150kg (at bodyweight of 100kg). But then I'm a bodybuilder, not a lifter and rarely lift fewer than 3 reps per set.