The answer is .. it doesn't matter what version you use, if you are using a device like the PAP2.

The main addition in the "voip" version of dd-wrt is SIPatH, a SIP proxy.

http://www.dd-wrt.com/wiki/index.php...#File_Versions

In short, you can use any version of dd-wrt that suits you, your router, and other requirements. The voip version is not necessary. I use the mini version, myself.