Hello, Looking for some help in choosing the correct car amplifier. For a combination of Sony speakers XS-162ES at front & XS-160ES at rear, which is a suitable amplifier among Sony XM-GS4 or XM-4ES? I require to get crystal clear sound only with some good bass. I am NOT looking for very loud sound. What are the extra things to get from XM-4ES over XM-GS4, is it only loudness or the output is far better in terms of clarity? Is it worth the price if I install XM-4ES or XM-GS4 will meet my requirements? If you can please let me know. Thanks!