Kid....is your current backpack designed for photo equipment or just basically a bag with straps? The photo BP's will hold alot of stuff. Mine is a Delsey Pro and in it I can pack photo gear for both of us....
2 - C-5050/PT-15's, camera inside the housing since it's in carry-on
1 - ULCS digital tray, Infinity arm, Inon D-180 strobe
2 - battery chargers and 10 sets of NiMH batteries.
Fiber optic cables, maintenance kit (o-rings, grease, dessicant packs, tools, etc)
1 - laptop
Fully loaded it's close to 35#'s so depending on the airline, I may check the strobe and maintenance kit in the clothes bag, but it does all fit in the photo BP where there are padded dividers I can customise.