A lot of the problems are always the result of the end users configuration of their computer and equipement, they environment surrounding their network, and of course, lack of knowledge and common sense.
People are very quick to blame everything and everyone else but themselves.
You have the same gateway that I have, using Aliant as the service provider. You will not see any signal gain by exchanging out wireless gateways. As stated in the above paragraph, you are going to have to re-think your networking environment. 40 percent signal strength is fine. I am sure your connection rate is fine as well. If your only using the PS3 for online content, you will be fine since internal wireless connections are in most cases, much greater than downlstream internet connections. There really is no need for mega super fast speeds on a gaming console, unless your hosting a lan party or using the ps3 to stream multimedia content, even then, your fine for DVD quality content.
Yes, i've had my share of problems with the dir-655, but they were not significant issues, and of course, acutal issues with the environment and the other computers and the people using those computers. The only significant problem I had with the dir655 was the shareport feature and in my opinion is a very bad implimentation of sharing resources using that usb port, however, that is my own opinion, and I don't use it, so problem solved.
If you are only getting a wireless router, to try and increase connection reliability to your ps3, I would instead suggest purchasing a repeater, otherwise, I would recommend a gateway that does simutaneous 2.5 and 5Ghz frequency. All my gaming consoles are hard wired, I turned off the gigasets wireless radio to reduce interference.