After much researching and tweaking I was finally able to get my wireless settings optimized for this Netgear monster and on par with the signal levels of the stock closed-source firmware.
I started my search with what the FlashRouters folks recommend but their settings do not even touch on the advanced settings.
Next, I discovered the recommended QCA Wireless Settings which were much better and got me most of the way there.
I finally was able to dial it in with the settings recommended here on the DD-WRT forum.