So strength is a misnomer as all must not exceed the maximum. That out of the way I usually find that placement is key to coverage. That is, the number of WiFi hotspots in basements is too high.
There are many tricks and tips to make what you have better. Did you look at your coverage and channels with an app like WiFi Analyzer? (that's what I use.)
You may find your neighbor is on the same channel.
Own a Arris TG862G/CT and am seeking a better model with a stronger WiFi bandwidth but still maintain the other features such as the telephony to be compatible with Comcast. Isn't there a stable unit under $200?