Steve, if you do ever go for a mastiff, and would maybe conider a rescue dog, this site is fantastic

http://z11.invisionfree.com/molosserbreedspart2/

they will be able to give you all the advice and help you could ever need too!

They have neopolitan mastiffs, presa canaros (sp), dogues, bullies, basically all molosser breeds on here that need new homes!