You're right mate. I only bought the big discs though not the calipers. For my needs they are more than up to the job. Infact, they are probably better that my old GT4 with 4 pots as standard and 315mm discs up front. It is a cheaper alternative to the 4 pot conversions which, unless you go on the track a lot are probably over kill. But, Highspec do these as well so the choice is still there.
I wanted DS2500's but, they don't make them to fit the standard GTIR caliper so Pagids are the next best thing.
Minor changes to the back i.e fluid, hoses and pad changes would suffice. As you say, you may not think they do much but, will feel the difference if they aren't working !