I went with these in my dash. I went through MANY 4” speakers, including pairs much more expensive than these, and these were the winners:

Amazon.com: Rockford Fosgate R14X2 Prime 4-Inch Full Range Coaxial Speaker - Set of 2 : Electronics

Amazon.com: Rockford Fosgate R14X2 Prime 4-Inch Full Range Coaxial Speaker - Set of 2 : Electronics

www.amazon.com

I drive them with this amp, which is powerful, clean and very compact. It lives on top of the passenger side kick panel:

Amazon.com: Rockford Fosgate PBR400X4D PBR400X4D Punch Compact Chassis Amplifier : Electronics

Buy Rockford Fosgate PBR400X4D PBR400X4D Punch Compact Chassis Amplifier: Multichannel Amplifiers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I use a Kenwood KMM BT318 head unit. Inexpensive, sounds great, has a good EQ and the built in crossover is excellent. I high pass the fronts at around 120hz, and my sub is crossed over at around 80hz. You can adjust the curve for both sub and mains.

You will need a sub. I built a box that takes the place of the parcel shelf, and installed two down firing 8” subs. Ports are also down firing, and parcel shelf is carpeted so it doesn’t lose its functionality. Sub amp is just a small, cheap mono amp purchased from eBay.

 

Thanks. Great suggestions. I'm not interested in waking the Neighbors when I come home late. Will those Subs be Overkill?

 

There are probably dozens if not hundreds of choices; just within the last few weeks I installed this JVC head unit (KD-SR86BT). Considering the simple speaker arrangement in the 560SL, sounds fine to me. Bluetooth connectivity, microphone for phone, CD drive, USB input, voice commands, etc. Operates the power antenna correctly, display color can be changed, so the manual says. Less than $80. (I'll never win a car show though).

 

Looks like a pretty simple operation. Did you notice a marked improvement over the Existing unit. Sounds like you didn't do Rear speakers; is that correct?

 

We're all here to confuse you more, @nshade
Bought my R107 a couple of years ago and the previous owner had installed a Clarion head unit, 4" speakers and amp and big sub in the boot. Sounded shit. So I adjusted everything. Still sounded shit. Threw all that out and installed a Continental TR7412UR head unit, radio and bluetooth only, CD and digital radio I'm not interested in. Polk DB402 4" speakers in behind the original grills. Cerwin Vega VPAS10" underseat sub. That was it, no additional amp needed, and once the Polk speakers had broken in it sounds quite good. An underseat sub will never give you the punch a boot box will give you, but it does fill out the bass really nicely, and apart from the non original head unit, the rest of the car looks unmolested. There is enough punch to still hear music top down. We rivnutted the sub to the bare floor and cut the carpet around it. You cannot see the sub looking in the back or front and it fits under a 1987 seat frame. Deciding on what to install is never easy though. Good luck

Soundlabs Group Continental Bluetooth Car Radio TR7412 UB OR
DB402 DB+ Series 4” Coaxial Speakers with Marine Certification For All-Terrain Vehicles | Polk Audio
Amazon.com: Cerwin-Vega VPAS10 10" 2Ω 550W Max / 200W RMS Powered Active Subwoofer Enclosure + Bass Knob: Home Audio & Theater

 

Some of this is dated (equipment wise) but it might give you some ideas.

107 AUDIO THREAD | Mercedes-Benz Forum (benzworld.org)

 

If you are looking for just an upgrade but keep it to the two 4” and a new head unit I am really impressed by these speakers: JBL 4”

I have the keinzle head unit you see written about on the forum and I think the look and functionality is great for a basic head unit. The only downside is bluetooth doesn’t show the song title and artist, radio does. The continental one mentioned above is very similar but doesn’t have the little chrome strips that I think make it tie in really well. Also nice that it doesn’t have disco lights and flashy BS, just a nice yellow tint that works on a vintage car.

If you want tons of bass and more than just clear loud mids and upper range than some of the options above are your best bet but if you just want a quick and easy upgrade then this is a great option.

 

My car has the original Becker 612 (late model) and the original speakers. Has anyone ever heard this radio through a decent pair of speakers? Is it any good? How does the sound quality compare to a modern radio?
I'm considering upgrading the front 4" speakers and adding some larger ones in the rear and am wondering if I need to upgrade the radio.
Also, has anyone ever heard this?

TRIBUTE-SERIES BLUETOOTH AM/FM USB AUX RADIO ASSEMBLY : EUROPA (LMKUU)

The Tribute-Series radio is undeniably the closest visual representation of the original Becker Europa and is packed full of today's popular features like Bluetooth, AM/FM Radio, Optional DAB Digital Radio, USB/AUX inputs and RCA Line-out.

www.retrosoundusa.com.au

 

I see, it uses the retro sound unit with a faceplate. I personally don’t like how the digital display is behind the tuner on this model. I have a similar retro sound radio in my Volkswagen. Sound is ok ish. Similar to a $75 Walmart head unit. You are paying for the appearance.