I am getting a slight knocking from the drivers side, sounds like it's the shock top mount, so will be replacing both sides, but as I will have it apart I'm going to replace all 4 shocks with new standard (cup pack) items, which leaves me with a decision of what springs to go for? Eibach, H&R or Cook Sport. I do a lot of miles 500+ per week so don't want to compromise comfort too much, what's your views/experiences?