done mine myself but it was a big job and you need two people to do it. It took me 4 hrs and im above average (7/10) with a spanner and ratchet.... IMO its a worthwhile upgrade to work with the twintercooler, you need the hoses from the S3 as well.
S3 cooler is cheaper than Pro alloy or THS (prob not as good but almost half the price and OEM)
The main problem i see is all of the above regardless of claimed efficiency are obstructed by the condensor (air con) rad which means the twintercooler is by far a better product based on the fact it has no real obstruction from atmosphere apart from the grille (and that has plently of holes in it lol)
S3 and Twintercooler are the favs by loads on here, start with S3 cooler and get Twinter later on if need be.