Well, I don't own an Alsvin but I've shifted from jdms to locals in the past 3 years.
And I understand your complain. The speaker and sound quality in general, offered by a jdm is much better. Infact in my case, I found that the two front speakers alone provided a better experience compared to my pkdms boasting a 4 speaker setup.
You'll just have to live with it, OR change the speakers and add an amplifier (to compensate for the shit quality screens) to enchane the sound somewhat