Do not dump flat bench in your routine. That may work for some people, but for the most part flat bench is going to make entire upper body grow when done correctly. I have a buddy that weighs 165 lbs, and bench's over 375. His ONLY chest lift is flat bench.
Like mentioned above, play with the grips. I just started using a wider grip the past couple of months, and I can tell a HUGE difference in shape already. A lot of guys use a narrow grip on flat bench so they can handle more weight, but really you're making your arms do a lot of the work and taking away from your chest workout...
Widen your grip, and try doing at least 4-5 sets. I switch my reps around, but i'm a big fan of 5x5. I used to have problems gaining size on my chest. Now i'm going up about 15 lbs a month on bench, and size is going throug the roof. Here is a small breakdown of my routine....
Flat Bench: 5x5 wide grip
Incline Bench: 8x4
DB flies: 4x10
Underside Cable flies: 4x12(for lower chest development)
I change it up about every 3 weeks, but you get the idea. Another good rule of thumb is, if you train Chest twice a week, mix up with core lift you do first. For me, I train chest twice a week, Monday and Thursday. On Monday, i'll start my routine with flat bench, and on Thursday i'll start it with Incline.
josh