Decline presses give you an advantage in leverage.
I don't believe in being able to hit "separate" either. The chest (Pectoralis Major) is basically one muscle, although in certain individuals with low BF levels, there 'appears" to be an upper and lower split.
Check out your anatomy books. The pec minor is nearly inconsequential and doesn't have much to do overall with chest size.
The Pectoralis Minor serves to move the shoulder area forward. This can be seen by shrugging your shoulder forward.
Exercises Exercises that work the Pectoralis muscles include:
Flat barbell bench press
Incline barbell bench press
Flat dumbell bench press
Dumbell flyes
Cable crossovers
Pec deck machine
Push-ups
Dips
I would stick with these. The declines also have a tendency to make you feel stronger than you really are, and can increase the BP inside your head, which in turn may be even more deservant of a knowledgeable spotter (which is a rare find these days)
Good luck.
Kick the declines to the curb.