With home theater you want you front 3 speakers {center, left and right} to be of matching timbre, so from the same manufacturer and the same model line, also some speakers don't play well when used as a center {I have noticed this with some bookshelfs I used, when I turned the center its side, sq was off}.
You are on the rite track with pictures, also model numbers will help, if your JBL speakers are not too hard to drive {and I suspect they wont be} you can run the front end phantom with no center and just go with a 4.2 system, then buy an AVR with preouts and dual sub capabilities {I don't have enough experience to say .2 avr capabilities are hugely important, but it seems to be nice to have}...
This model would work
YAMAHA RX-V773WA 7.2 Channel Network AV Receiver w/Wireless Adapter | Accessories4less , it would allow you to run your amps to the 4 speakers and then hook in both subs...
I would personally only run an amp for the fronts and let the avr power the surrounds, its much less wiring. and since them Crests are pro style amps, you will need a pair of converters so the RCA preouts from the avr can plug into the xlr bal. inputs on the amplifier... something like this will work
Amazon.com: Pyle PPRC-X05 Dual 5ft. Professional Audio Link Cable XLR Female to RCA Male: Musical Instruments .
keep in mind, sometimes it may be better to sell of what you have and buy a decent front sound stage that is made for home audio, but lets start with some pics, model numbers, and maybe some room dimensions, we will get your best bet figured out..
Thanks and welcome...