I'd say either the Amsoil Series 3000, 5w-30, which I think is their best formulation right now, or the Redline 5w-30 which I'm very impressed with. Those are also going to be the most shear stable 5w-30's out there, simply because they use higher molecular weight basestocks than cheaper, PAO or group III based synthetics ....
The best 5w-30 you can get for $4.00 per quart would be Mobil 1. There are also some excellent Group III based, 5w-30's and 5w-40s available for $3.75 per quart in gallon jugs. The Petro Canada stuff is exceptional I think ....The Schaeffers S7000, 5w-30 is far and away the best synthetic blend I've seen - if you get it in bulk I think it's around $2.50/qt.
Tooslick