Front Air Suspension Replacement Question

[simplx5]

I will be replacing the two front strut/airbag assemblies on my 05 4.8is. From what I've been told the ones currently on the car are the originals. I need to replace them not because they aren't working per se, but I'm getting a clunking noise in the front left. Multiple mechanics have determined that the clunking is not coming from any other suspension component. I may look to get OEM, but would like to avoid spending the $$$ on them if someone can share their positive experience with an aftermarket brand. Please provide name and miles driven the aftermarket. Any help is appreciated.