My goal is to have quadrophony on my DVD player, that means i don't need centre speaker, but since it's 4 channels only, would there be any bass or would i have to make additional .1 channel? Either way i have one 4 channel and one 4.1 channel wave standing by...

So my question is what software do i need to burn a quadro DVD that will play nice on my DVD (with centre speaker silent)?

What source are you intending to put onto the DVDs, just out of interest. You will still have bass without the .1 channel being used. Only difference is it'll be directed to your main speakers not your sub unless you have bass management set-up differently.

As for how to burn DVD-As, there is plenty of useful info on: http://www.quadraphonicquad.com/forums/
Several of the guys on there convert old 70's quad vinyl/tape to DVD-As (for their own use, nothing illegal). There's a whole forum section devoted to such matters.
I believe you don't even need to use MLP lossless encoding if you stick to 4.0, but I'm no expert.

AFAIK you can feed your encoder and left the unwanted channels blank (4.0 will depend on your amp´s bass management - as pointed out before)
One thing you should keep in mind is to watch the channel order