jcepiano,
Good question. If you have a straightforward single vision lens, I think you are going to get a
comparable lens at Costco as what you will get from an independent eye doctor.
You can see
my review of the Crizal Avance coating. Just to be clear, the Avance is a coating for the lens, not a lens in and of itself. It is a very high quality anti-reflective coating that also is durable, scratch resistant, and easy to clean. I honestly could not tell the difference between my Crizal Avance treated lens and the lens and anti-reflective coating I got from Costco. Either provider will probably give you a standard polycarbonate lens, as I would think you'd have no benefit from a high index lens, and a high index lens may actually worsen some of the halo's and other problems you experienced with the Trivex lens. I'm curious - did you have an anti-reflective coating on your Trivex lens?
One thing I would suggest is that if you go the Costco route, before ordering them, ask what their return policy is if you aren't satisfied. In the past, most items at Costco are able to be returned if not satisfied, and they may provide a similar guarantee with their lenses. If that's the case, you'd definitely have little to lose by going that route.