The bad n news is that you probably won’t be able to use your JBL speakers with that Panasonic. It’s a so-called “home theater in a box” (HTIB), and with these things very often the speaker connections use proprietary plug ends that aren’t compatible with other standard speakers. Even if you could get around that – say, by doing a lot of wire-splicing – often the speakers that come with HTIB have unusually impedance ratings, which means other speakers may not work well with the amplifier.
Since you had an AVR before, your best bet, if you really want to use your JBL speakers, is to stick with that route: Return the Panasonic, get a new AVR and a stand-alone blue-ray player.
Regards,
Wayne A. Pflughaupt