Can you explain the installation of the rear set a little? Glad to hear you are happy with the upgrade!
Basically, it goes like this:
You have to remove the side sills and unplug the connector.
Move the seat all the way forward and unclip and remove the back seat bottom.
Then you have to pull three trim pins out of each lower rear side panel - my suggestion - buy some extras as they will get damaged and will not be reusable - Buy 6. Throw the old ones away.
Then you have to pull out the side panels. The more pins from the back deck cover, then pull the back deck cover itself. Then you have to unscrew the speakers and pull them out.
The rest is just the reverse of it. There are some walkthoughs with photos of how this is done on this forum and others.
This is something you want to get right with a speaker you will be happy with as you will not want to do this install ever again.