RPZs are an expensive bullet. They also take away water pressure you might not have to spare. Cheapest is to raise them, and figure out how to hide them. (you always wanted to have a miniature windmill in your yard, didn't you?) Maybe there's a place further downstream to install a taller vacuum breaker.
And yes, the upstream AS valve is useless.
One thing about the brass AS valves that can come in handy, is that if you do install an RPZ, and find you have low pressure problems, replacing the Champion valves with standard underground valves can buy back a fair amount of pressure. Those Champions (especially the 3/4 inch ones) have high pressure losses. In fact, with two AS valves replaced, you might actually gain pressure with this work. (which is why you'd want to use valves with flow controls, for easy matching new with old)