Headlight brightness

[cooperconnelly]

Hello I am after some advise .I have some head light bulbs in but they were not very bright so I changed them to Halfords 150% brighter bulb 

now when driving the car it’s like I have no headlights on at all , main beam work really well and is bright .but when driving the lights are on but not lighting up the road 

Main dealers say it’s the alternator which’s £900 pounds , any ideas what might cause this as I am struggle to see the road when driving