The Hosa CMP-159 cables can be pulled apart, but that connector (1/4") will not work with the Airmotiv 6.
Airmotiva uses XLR (balanced) or RCA (unbalanced) connection
http://www.amazon.com/Hosa-CMP159-Stereo-Breakout-10-Feet/dp/B005HGM1D6/ref=sr_1_1?ie=UTF8&qid=1462489663&sr=8-1&keywords=3.5mm%20to%20trs&tag=viglink20246-20
I'm guessing the Belkin 3.5mm to RCA cable might split for about the first 12" (maybe)
http://www.amazon.com/Belkin-Audio-Cable-Splitter-1-Mini/dp/B00004Z5CP/ref=cm_cr_arp_d_product_top?ie=UTF8
The JBL and Airmotiva come with two separate amplifiers built into each unit.
The 5+ comes with at most one amplifier driving each unit.
Not even sure how discrete the amps are. as the 5+ uses one unit to drive the other unit.
The Monoprice 5" studio monitors come with two amplifiers built into each unit
Audio quality wise the Monoprice 5" studio monitors ($170) should be easily at least equal to the Audioengine 5+ ($400)
http://www.monoprice.com/product?p_id=605500
For less money then the Airmotiv 6 ($500).
You can get Monoprice 5" monitors ($170) and a Monoprice 10 "sub-woofer ($220).
If you did get the Airmotiv 6 units, I really doubt you would have any reason to want to return them.