Zipp and Enve are great, but I don't think they're putting a lot of R&D into rim brake wheels these days. I also would caution against investing that kind of money on a rim brake bike unless he's totally committed to keeping it for many years. I definitely wouldn't be buying fancy rim brake hubs at this point.

Those November Rail 55 wheels look pretty good. With Bitex hubs they're $930. This is comparable to something you'd get from Light Bicycle. This is the price range I'd probably shoot for.