As someone who is newer myself I would also suggest going with someone who sponsors the board. I only have two black power cannons, the first one I purchased for cheap off ebay from someone making them themselves, the second I purchased from armorer77 a board sponsor.
After my experence with armorer77 I don't think I will ever buy a new cannon again unless it comes from a board sponsor (and I will have a hard time not going back to him after the service/product he gave me). My mortar from armorer77 will more than likely be proudly displayed on my desk as it is beautiful, it is a true replica/tribute to the past. The other one doesn't look like full size real cannon, sits in the corner of my garage, and needs to have a new carriage built as the last time it was fired the carriage self destructed due to poor quality, design, and construction.
The first one I got does go boom and the barrel is strong, but that is all it has going for it... I won't ever fire it again until I have redesigned/rebuilt a carriage for it as I don't feel safe firing it knowing that it will fall apart. I have all the confidence in the world with my mortar and I have no doubt that I would feel the same way with any cannon purchased from any of the sponsors.
I hope I don't sound too much like a leg humper but I thought that you might like to know the experence of someone who was brand new not to long ago and had both good and bad experences.
Stuart