First off, just to be clear, you can't "isolate" a portion of the chest. Not that you used that word, but usually this sort of question is getting to that. You might put a little extra emphasis, but mixing angles, grips, etc, is just to give the chest, as a whole, different stimulation. It works as one muscle.
Secondly, I know a lot of people use a 45 incline, but, in my opinion, that's a bit too high. That's getting to the point where it's going from a pec-dominant push to a delt-dominant push -- more along the lines of a shoulder press. I've always used 25-35. It's enough that it's a very different experience from a flat press, but remains a chest-dominant lift
On another note, I had a neat idea for a incline chest exercise, which you might try. I haven't tried it yet. It's a cross between corner press and incline press:
Grab an olympic bar and place it in a corner. Set up an incline bench in line with the oly bar (doesn't matter about sides because the oly bar can just pivot to each side). Raise the olybar and lay down on the bench to get into position. Now, with one arm at a time, press the bar from your incline position. So, basically, it's stuck in the corner on one end and the other end is close to where you're holding it (with a neutral grip, of course) and then you bring it down and press it. a different approach to a unilateral incline press. In this case, your arm will simply be going up and down, not inwards like when using DBs. Nevertheless, the chest is still working