Hi
You would get a bigger response on the MK6 section, plenty of topics if you search too.
Some of the big names in remapping are Revo/APR and GIAC, I have Revo but also had an indy remap on my MK5. There are independents such as Shark and Carbon who develop their own remaps.
As for the link, I haven't heard of maps from this firm and it isn't clear whether they are offering their own code or acting as a reseller for the likes of Revo et al.
I would try and pick somewhere within a reasonable distance in case you have problems post remap, a decent tuner will be able to assist in these circumstances. Also I would it would be preferable to have the remap undertaken at a facility with a dyno so that you can see before and after results.
Are you wanting to upgrade the brakes and other parts for tracking? I probably wouldn't take my daily for regular track days. It's a whole different ball game setting a car up properly for the track and you will be exposing the whole car to extra stress.