Our benching is a little different since you hit twice a week, but from everything i have done, these are the pairings i have benefitted the most from:
1. flat barbell, incline barbell
2. flat barbell, incline dbs
3. incline barbell, flat barbell
4. incline barbell, decline barbell.
Dont get caught up on the flat db thing. The big problem is that if you stick to them for any period of time, they will go up, but your flat barbell will suffer when you get to the higher weights.