Upgrading "premium" factory audio
 

My 2006 Lexus IS350 did not come with ML, but rather the base "premium" audio which IMO sounds not premium at all after having a BOSE system on my last car.

I've gone through countless posts trying to figure out which is the best way to improve my system, but am left with more questions than answers.
Many people have advised against upgrading due to the complexity of the factory system being all integrated together, and upgrading some of the speakers and keeping the OEM head unit, amp, sub etc might end up sounding worse. So, I've looked at other options such as the JBL MS-8 as a DSP/amp to improve the sound quality, but after calling a few local car audio shops many technicians have told me this probably won’t make my system sound that much better, and it’s a very complicated and expensive piece of equipment to install.

One shop I called advised to just install an inline power amp for the sub and get a bigger better sub-woofer with an adjustable low pass filter, and phase control. He mentioned this would free up the other speakers to produce upper frequencies much cleaner.

Can someone advise what would be the best simple upgrade to do? I’m not looking for a complete system overhaul, but I’m looking to do something to improve this weak sounding "premium" system.
My goal is to have a louder clean sounding system, with just a little bit more added bass.

I would suggest dropping in for a free consultation to determine the best course of action for you & your car. We can look at the settings that you have on your set-up to try to tune it for you and make some suggestions to improve the things that are missing.
Choose the shop that is best suited to your needs (Burnaby or Coquitlam) and make a half an hour appointment for us to put the meter in your car to see what is going on.
It's amazing at what a real time analyzer can show us what the untrained ear cannot articulate.