Tube choice for 71 Bug

[Bob McSmith]

Used to have a VW bus with tubes under the seats- loved every minute of it. 20 years later and I'm looking for something for my VW Beetle. There is enough room behind the rear seat for any system so size isn't an issue. I'm looking for recommendations- not looking to blow the doors off- just good clean bass with pop. Listen to mostly rock- classics to today.

For example- the 6" 200W is same price as 8" 100W. Does the larger speaker make up for less power? In essence, do they sound basically similar, so it's a size issue?

Do to the small size of the interior do I need more than a 6"?

Any guidance you can give is appreciated. Thanks