I think the point is that at the scale you're working at now, anything larger or more expensive than the WonderMill Wonder Junior just doesn't make sense. It's about $250 with the drill attachment, though I would try to motorize it using the optional pulley) and you're not going to get better price/performance in a pre-grinder.
This doesn't make a "proper" liquor. However, anything you can do to reduce the particle size before you put it in your melangeur is going to speed the process up considerably. As Ben notes, warming the stones gently is also a good idea (use a small resistance heater that doesn't get hotter than about 100F, put it in the bowl a couple of hours before you want to use the melangeur - or overnight - and cover with something that will help keep the heat in.
From a tech perspective I think colloid mills are a better bet for oily products like cacao than hammer mills. I would be careful, however, about buying machines from China. There's a thread on the new melangeur from Kudvic where Victor talks about some of the issues he had with Chinese-made machines that led to his developing his. His experience echoes mine pretty closely.
clay - http://www.thechocolatelife.com/clay/