While the stock radio reception is garbage, it is not the head unit that is bad, it is the antenna. Changing to a different am/fm unit is most likely not going to improve your radio experience from the stock one. I may put another antenna on mine, the one in the window just does not cut it here, too many trees, mountains, and hills.
This is my only vehicle newer than 94, and though i had seen the aux port and the SD card slot i still lamented CD because that is what i have always used, and use in my shop, etc. ...Then i tried dumping stuff on a card, and well I can have a whole library in the van without having something that the inevitably will be sandblasted, dropped while fumbling etc... I mean i knew that this was possible and an advantage, it was just not something i had done before, and i guess i am slow.
There is a certain comfort of going through vinyl cases, or cd jewel cases and picking out an album to sit down and listen to, I get that, but I'll do that at home when i can focus on it, and not while i am driving.
I do not use a cell phone, but my relatives that borrowed the van hooked it up to their phones via bluetooth for music, etc...
I don't know how many cds you have, but sitting and ripping your songs off their disks onto a computer, and put them on and SD card will probably take less time than figuring out and putting in a new head unit. It will also save you the time of looking for, and monetary cost of a new head unit. This conversation prompted me to rip more from cds that i had not gotten too yet while i am sitting here. I assume that you have a computer. Set like 3 cds by the computer and copy them to disk and move them gradually over to an SD, or a few SDs... I just did some Charles Mingus, Taj Mahal, and some Johnny winter and it took about 30 seconds per song i would say.
From the SD card, the stock stereo sounds really pretty darn good for a stock stereo. I was surprised.
I know, not what you were asking, but yea I was thinking along the same lines as you and then... realized maybe the new tech might work out, and in this case it did.
I was going to put a cd deck in my 80 series landcruiser, but am looking for an sd option now as it worked so well.
Some metris's may have more deadening in them, but mine would need something more in it if i wanted a lot of bass and did not want the whole van to resonate with it...