If in doubt----- I recommend the full upgrade to the Radio 10 with all 5 speakers---- two tweeters, two midrange and one sub....
All the wiring, and mounting is done... .... if you think the system is too muddy, too tinny, or just flat...then for not much green you can change out the factory speakers to better quality same size "bolt em right in"
If needed, add a modest mono amp to power the sub... not to hard nor very costly.....
I am not talking about making a Sound Pressure Level competition system....
You would be amazed at the deals you can find in Pawn shops on this kind of stuff...wink wink