Volfenhag might be the better choice of the two. I have seen a lot of people putting Volfenhag down here on ecoustics but I have seen just as many praising them on other forums so it's hard to get a clear picture on their amps.
since your subs are 4 ohm SVC it also depends on how you intend to wire them. If you go parallel (creating a 2 ohm system) I would definitely stay away from the Sony amp as I have heard they don't handle heat well. If you go series then I'd say the Volfenhagen would work fine for you. It's been a while since I've worked electronics (old Navy avionics tech here) but I don't think you want to put a lower impendence system on your amp (ie .. if you bridge an amp at 4ohms .. you don't want to put a 2 ohm speaker system on it).
Someone correct me if I'm wrong .. as I said before .. it's been a while since I've done electronics. I'm a programmer these days. Not much call for them up here in Bismarck, ND. Maybe I should get back into avionics and see if there is a job at the airport.