Hi Karly, and welcome!
Why don't you list your current spec and we'll nit-pick it for you!
If you're a big music fan and don't like making changes to the car after it has left the factory, then the Harmon Kardon HiFi would be a good option. However, the BOOST option may be good enough on its own.
The seats, however, are going to be much harder to have changed later. I have part leather seats in my current tin top cooper and I can't imagine having just cloth now. I've spec'd full leather in my
MCSC on order.
Other things to consider are heated seats, and whether or not you want a wind deflector.