The Bean-Animal overflow with a sump, IMO, is the way to go. I work a lot with plexiglass, but I doubt I would make an Bean-Animal type overflow if i wanted it quiet, because making the teeth in the inside portion needs to be angled to obtain a quiet flow. I just purchased an 800 GPH overflow from Modular Marine. High quality, really nice looking. Their site is closed down over the holidays, but their products can be found on eBay They will respond to emails, but it may take a few days. I realize you mentioned your looking for a certain maximum dollar value, but IMO it's definitely worth the wait to save up for a well designed overflow.
With that said, building your own overflow would be much easier with Plexiglass. Here in Sacramento, Tap Plastics will custom cut sizes to what ever you want, but I'm not sure if you have the same options in your town. Use 1/4" thick plexiglass, it's makes it much easier to figure out the dimensions. Price out everything you need, bulkheads, plexiglass, hole saws, etc, then compare the price with Modular Marine's overflow, which comes complete, except the piping.