Troy, I would think if you can flat bench the 42.5kg dumbells you'll be able to rep 100kg pretty easily.
I much prefer benching with dumbells over barbell, but i havent done flat bench with dumbells in a fair while because i have been doing PPP.
Im not arguing that your upper chest hasn't grown since you have done more incline benching, im just stating what the scientific research using emg has shown...
Either way doing a combo of flat and incline bench is your best bet i say, i do both on every chest day...