Aftermarket speakers with OEM AMP?

[ZoliWorks]

I have the factory 10-speaker system in my Mk5 Jetta, including the factory amplifier under the driver's seat and a RNS 510 head unit (retrofit).

The speakers are now almost 20 years old and a few of them are starting to fail, so I'm looking into replacing them while keeping the OEM amp and RNS 510 for the factory look/integration.

Has anyone had good results replacing the speakers while keeping the factory amplifier and head unit? I'm mainly interested in speaker recommendations that work well with the OEM amp.

My other Mk5 has Hertz Dieci speakers running off the stock head unit without an amplifier. They sound pretty flat compared to when I had an aftermarket head unit installed, which makes me think the OEM radio doesn't really like the 4Ω aftermarket speakers compared to the factory setup.

I'd prefer not to replace the RNS 510 or add an aftermarket amp unless absolutely necessary. Has anyone successfully upgraded the speakers in this setup?

[mjmallia]

I have the 10 speaker system also and replaced all the speakers with Pioneer in the front doors and Kenwood in the back doors.  I did keep the original front door tweeters as they sounded better to me, but did leave the inline capacitor thinking about it when it was connected to the OE crossover.