Hi and welcome.
Nice car and in the BEST colour of course

I have standard sound system with iPod and it does the job for me but many other owners like to go the aftermarket route.
OEM Sat Nav looks good, especially the new RNS510 touchscreen system but the DVD MFD2 system also does the job - only real drawbacks IMO is the lack of full postcode search and a somewhat old-tech 2d mapping display by todays standards.
Monza II's are the dogs and the aftermarket one's you are looking at are competitively priced. Choose your tyres carefully - there are different opinions as to good/bad.
Lot of good threads here so do some searching and you will get a flavour of what's been done by other members. Me, I'm into standard spec all the way - too old to mod

See Hurdy just beat me to it - like minds etc

Cass