I have two Staffies they are about 18 kg, I feed them 100grams each of Euka a day mixed with 100grams each of mixed and cooked chicken mince, mixed vegetables and rice. Plus they get bones and chicken wings during the week.
I put them on this diet after one of my staffies had a cruciate ligament done and they have both lost nearly two kilos each and their poos are much better and I would say their general health is better. I have found the Euka to be great, and I also had the problem of trying to find the right and best food for them and it all becomes really confusing as everyone has different ideas. Euka is more expensive than the supermarket brands but it works out not too bad when i did the sums, plus one of my Staffies was the fussiest eater, but now she licks her bowl clean. Hope this helps.