Maybe see how you find the standard brakes after the remap. More power doesn’t necessarily mean you’ll need better brakes if you’re a decent driver! If you do want an upgrade in the future the 8v S3 / mk7 R setup works well. Bigger piston, bigger disc, and not so big that you’d have to mess around with wheel spacers to clear your wheels. They should even fit behind your 17s.
As for wheels, be careful not to end up with a set of 18s that weigh significantly more than your 17s. Any improvements from your power/braking/suspension upgrades could potentially be ruined by adding a load of unsprung weight and rolling mass. Arguably sticking with your OEM 17s would be your best bang for buck decision, but look into the well made lightweight options for 18s like BBS, Oz, etc. If you must get 18s, don’t end up with heavy replicas. Obviously OEM Monza 18s are a sound option. Just make sure they’re real!
PS4 really are an excellent tyre. Definitely worth the money and just like fitting light wheels, good tyres will allow you to reap the full rewards of your overall mods. More engine power is useless if you’re forever spinning up on boost, better suspension is useless if your tyres can’t cope with the extra lateral force in a corner, and more stopping power is useless if the tyres just lock up. You get the picture.