The nature of what you're trying to do is chaotic and no particular mixer necessarily lends itself to a particular 'sound' beyond tiny, tiny minutiae that will only be relevant once you have spent some time playing, experimenting and feeling out the equipment you end up with. Not only that, but it will eventually be bad for your mixer to run such hot signal through it over and over again, so, the cheaper the better once again. I know it isn't the answer you're looking for but the best thing for you to do is grab ANYTHING you can as cheap as possible and simply experiment.
That said, a mixer with more ins/outs/auxs the mixer has will provide you with a greater number of channels to play with. The more EQ = more variation in sound so in theory a bigger mixer will give you more options.
When I first started messing about with this stuff I just got a small Behringer. Maybe start there? Is there any particular direction you want to head in with no input mixing? Balls out harsh noise? micro improv? somewhere in between?
