You converted to 2channel or 6channel wav? Because if you want surround then converting to 2channel kinda defeats the whole purpose of having surround.
Don't think DVD2SVCD supports multichannel mpeg audio, but then again I have never used it. If this is the case then you would need to convert the audio seperatly. For this task I would suggest Hypercube, which I understand accepts AC3 as input so no need to create temporary wav files.
Does your DVD player even support surround sound SVCD's? Because my understanding is that not many do. If not then if you have a prologic2 or similar amp setup and did a surround2 downmix in headAC3e, then you should still get decent surround sound.