I honestly don't find it all that bad? With a noisy car etc. Like its not Mark Levinson... maybe fit for purpose is a better term.
The issue with the inline amplifiers is that if you amplify the output from your head unit you are not only amplifying the signal you want but also all the noise you don't - your amplifying the weaknesses of your basic headunit. So if you looking for the best sound quality I would make the switch as Brigsy has said to a better quality head unit.
Theres a new media only Sony which is top class, but I' sure all the big boys have good offering now. I've had a few Pioneer DEH-P01's in various cars and the DEH-P8400 before that which always sounded great for the day but now tent to just like the look of the original OEM stuff.
I'm the same as you. I don't think mine sounds bad at all in my 182.
I've seen alot of people over the years say the head unit and speakers are crap.
I remember years ago one of my front speakers blew in my 172 so I bought one from a 172 cup on ebay. It was alot lighter with a much smaller magnet and the sound wasn't as good as the original.
I know jack s**t about audio. But from what I've read there are 4 different headunits across the 172/182 range.
PH 2 172s had a cabasse auditorium 2 x40w tuner list head unit.
The 172 cup only had a 2x22w tuner list head unit and cheaper, lighter speakers.
182FF's like mine have a 2x40w cabasse auditorium update list head unit, probably top of the range?
182 cups and Trophys also have an update list head unit but less powerful 2x22W. Maybe the speakers are also the cheaper, lighter versions same as they fitted in 172 cups?
Excuse the long winded post.