To answer the question about good quality affordable regulators, the good news is that almost any regulator model made and sold by a major manufacturer will work just fine for recreational diving. Too many divers (including myself
) get hung up on the particulars of regulators, and believe me there is an absurd amount of hype involved in the design and marketing of modern regulators. Don't forget, just a few decades ago professional divers were routinely making extreme dives on regulators that some of today's salesmen would tell you shouldn't be used in a bathtub.
To me the best way-by far- to save money and get good performance out of regulators is to buy used. Novice divers typically need an experienced mentor to guide them in buying used regs, but with the right guidance the risk is very small that you'll end up with something that isn't easily maintained and made to work as new. A best buy IMO would be a scubapro MK5 or 10 with a 109 2nd stage-one of the greatest 2nd stages ever, and a GOOD regulator tech to rebuild and tune these. There are all sorts of other choices....
For new, one of the regs that commonly gets mentioned as a best buy is the aqualung titan. This regulator is descended directly from the USD royal aquamaster, then the conshelf, etc...and it is a simple, proven design.
The balanced/unbalanced discussion can be found on any number of threads. The short story is that all modern diaphragm first stages are balanced, some piston regs are, some are not. It really does not make a great deal of difference; balanced 1st stages are simply not affected by (or compensate for) changes in tank pressure. However, unbalanced piston 1sts like the MK2 have a VERY SUBTLE loss in performance at very low tank pressures, such that most divers will not notice anything until the tank is well below 500 PSI, at which point a smart diver is back on the boat; and a not-so-smart diver might appreciate the reminder that gas is running low. With 2nd stages, the difference between balanced and unbalanced is even more subtle. In this case, changes in intermediate pressure (from the 1st stage) do not affect balanced 2nds.
The most important thing, IMO for new divers searching for their first regulator is to not fall for some of the BS hype that seems to permeate the dive gear industry. Buy something simple, look for a design that has been around a while, and stick with brands that have proven long term support of their products. One of the few things that can really cause a regulator to become unusable is if you can no longer easily get rebuild parts for it.