Thanks for the detailed reply
I also somewhat feel that the amplifiers are week point... And yes I got them installed with the fusion wiring kit. I am getting a good bass but the audio quality is not satisfying as that day they hurried up so the settings are yet to be done.. I will go there tomorrow and get it fixed up.. Kindly recommend the amplifiers please. The current setting is that he has out paired each amp with two speakers and one subwoofer so that there is no load. Kindly comment on that also. And to get better output what do you recommend should I remove the sony subwoofer and use just the jbl and pair one amplifier with it and other with the speakers..
Do look up on both the amplifiers and let me know what all settings are there, I will help you. Installers basically jack up the bass with the amplifier's settings which is harmful for the subwoofer (if it cannot take all that power) and amplifier (overheating issue).
If you are ready to change both the amplifiers, get 2 four channel amplifiers. One to drive your speakers (which should have minimum 55w x4 RMS power) from any good brand like Kenwood, Pioneer, JBL or even Sony. The other one to drive your subwoofers (2 channels bridged for each subwoofer) which should have slightly higher rating around 70-80w RMS per channel. You can select the brand and power output depending on your budget. Price would start from 4k anyway per amp.
Regarding the load part, this is where he has done it wrong. It would not help with the load in the current wiring also as the bridged output of the 2 channels (of sub) of each amp are actually 2 individual single channel outputs combined together. Infact this is messing your sound quality as one subwoofer is getting more/less power than the other as the amps are not having the same specs (or are identical). Same case with your speakers also, one set would be getting more/less power than the other. Get all 4 speakers on one amplifier and both subwoofers on one.
See what price you can get from the Sony subwoofer. You can exchange it for a grey market JBL subwoofer (same model as what you have) and enjoy your music! It is because 2 of your channels would be left idle if you use only one subwoofer.
You know what I would personally suggest?
Sell off both the amplifiers, sell of the Sony woofer.
Buy a 4 channel amplifier from good brand with around 55w RMS per channel and pair all the speakers with this amp. Next buy a 2 channel amp with 70-75w RMS and put the JBL subwoofer on it. This way you'll enjoy your music in great quality without mess.