Yes very much so.
The better your tyres grip the more energy you can transfer to the brakes.
You could have the best brakes in the world, but if your tyres have bad grip you will never release the potential of the brakes.
As some others on here have already said I have the Ksport kit on my track car. I have found them to be reliable and so far had no hassles.
Yes they are a cheap kit and lots of people frown on them however to me they were a clear marked improvement over the UK's I had on my previous Supra and the Track Supra, mainly for the pedal feel, not to mention they are a lot lighter which helps with reducing unsprung weight.
Its surprising to see peoples reactions in the car, they always comment on the how savage the braking is and are always surprised it is a cheaper kit.
However that said, my car is set up properly for the track and I am using descent pads, fluid and rubber so within reason similar braking could be achieved using UK's.
I will upgrade to an AP racing setup one day as it seems KSport and other cheaper brands change their designs from time to time so this scares me with part availability.
However for now they have been as good as the other more expensive setups I have been out on track with.