Another suggestion for the box. If money is a concern take a look at the Aqualung Titan mentioned by groundhog. You probably would not notice any difference in performance compared to the more costly regs. I know you don't want anything 'cheapy'. However, the Titan first stage is extremely high performance and bulletproof. The second stages that are presently offered with this reg are the downstream light weight plastic types similar to those used on the high end models.
Don't worry about claims that one model breaths easier than the other. Lakemount, all of these modern regulators, including the modestly priced Titan, are so easy breathing and generally high performance that the average diver would not know the difference. It takes a sophisticated test setup to discern these differences but any of the above are dependable and deliver plenty of air to 300 feet. You should look for a well known brand which is comfortable and reliable. It should be dry breathing, light second stage (in water), flexible hose, multiple LP, HP connections, abundant service facilities, good reputation. Any of the above meet these criteria.