Best retrofit Nav

[Alol]

Hello to all as a newbie on here........
Just returned to Scirocco ownership(was still in the brotherhood- Audi 8p S3)
This question probably being asked on here many times but had a quick look in the FAQ and couldn't find it.

Looked at a few before buying but ended up prioritising the pan roof/Candy white. Typically all the non proof examples had nav/PDC. The one I chose didn't! Not particularly bothered about PDC but would like to retrofit Nav. Gather the OEM unit is the RNS 315. Is this a good unit in that I can easily upgrade to latest Maps etc. One of the best aftermarket options i gather is the Kenwood 518? Like the sound of it but don't really want to spend near 900 notes on one....

[Zanic L3]

Just use Waze? It's much better. Get an apple or android car play thing if u want to have it on the big screen.

I wouldn't bother with getting an outdated VAG navigation system

[Alol]

I just wanted an integrated system. With the 315 and updated does it afford a 7 figure postcode search facility?

[Alol]

So if my car has the shark fin on the roof does that mean I will not require an aftermarket GPS Antenna (a la Fakhrir)
Really not bothered about having an all singing all dancing unit with apple car play etc etc