Welcome Mikergti

The Standard speaker system in my opinion is relatively poor
If you look at my project thread you will find a post on the sound system.
http://www.golfgtiforum.co.uk/index.php?topic=76660.0As for a company to fit said system - where are you based? I used a company in Sheffield called Source who have a good rep when it comes to sound systems and installs.
As RR says APR, REVO and Bluefin are the remapping companies that most people use. In my experience APR and REVO have a better rep than Superchips as having more thoroughly tested remaps (although this is a hot debate, so I'll say no more

)
I'm sure you'll enjoy your GTI when it arrives

Oh and as for the Recaro's I'm a 6ft and 14 stone ex ruffer bugger and I fit in easily - if snugly into them. The only extra consideration is that the recaro's dont have side airbags in them.