I am parting out my 98 mk3, the speaker sizes are the same ( i think) you can have my setup for a fair price.
here is a link to my listing. And if your close enough in PA to the MD boarder you can come pick them up too!
Jetta MK3 part out contact me for price for the parts you need
there are a few things you need to know. RMS is total BS, most stuff is all marketing gimics.
you want to know how many watts things are rated for, then get an amp for it.
I have a mini inline amp for all 4 with good quality speakers. I also have a big sub in the trunk if you want, but the headunit and speakers are nice. PM me for details.
Max wattage is typically total BS. RMS wattage is usually pretty accurate.
I'm running JBL GX600Cs in my mk4 at the moment - just in the front doors. Nothing in the rear doors and a modestly powerful sub in the boot. I'm very impressed with them, a little bright so they need taming a little with the head unit EQ but overall great staging and clarity and hold their own down into the mid-bass range as well. They do OK on head unit power but, like almost all speakers, really come alive when given proper power from an amp.
Previously I had JBL Stage 600CEs - great overall budget speaker, not quite as powerful on head unit power but more balanced and required less EQing get them sounding alright. Also had Edge ED306 which were honestly alright once amped considering they're at the very budget end of the market. My current GX300Cs are the best overall speaker I've had yet, which isn't surprising seeing as they cost what my previous two pairs of car speakers cost combined.
The GX600C is the component version, so you have a mid-bass speaker and a smaller tweeter. I 100% recommend component speakers for front doors. If you really want speakers in the rear doors then go with coaxial speakers. The tweeter is built into the main speaker. Two-way is fine - anything more is marketing rubbish. They're easier to fit than components, but you lose out on a little sound quality especially in the high end.
I mounted my amplifier in one of the cubbies you get in the side of the boot/trunk on wagons and trimmed the rest of the cubby with carpet so it looks nice when you open it up.
Once the door is clicked into place you have no idea it's there. It runs the front door speakers and the 300W RMS sub you can see pictured, which sits in a sealed enclosure. I don't bother with rear door speakers as I don't often have rear seat passengers, and they can mess with your sound stage unless you fade to the front whenever you don't have rear passengers.
You can see most of my build here:
https://imgur.com/a/3Zug9eu
It doesn't include head unit installation but there's a ton of information about basic head unit swaps on mk4s all over the internet if you want to go down that route. It does however show how I fitted the speakers to the front doors and how the amp was installed.
