The truth is there is no regulator that is better than the others.
Any double gauge CO2 regulators works for our purposes.
You can get a regulator only for $45 (shipping included in this price)
off ebay. That is the cheapest you will find that you can order and
receive in a normal way.

I'd like to hear from anyone about a specific brand being not good for
what we use regulators.

What really makes a difference is the needle valve. The best for the
least money is the Clippard MNV-4K2.
http://www.clippard.com/store/displa...sp?sku=MNV-4K2
Not the most precise control of the CO2, a small turn of the knob
results in big changes of the CO2 flow. But it is a reliable valve
and will not cause fluctuatons of the CO2 bubble rate.

Buying it from Clippard directly will be a total of $25 because of
their handling and shipping. Specialized online aquatic stores sell
it for about $20 and there will be shipping and handling too. So
either way - it will cost at least $25. Well worth it.

MarineMonsters sells it. The 2 other companies that sell it are not
reliable at all, but you may have good luck with them.

The easiest way is to buy an already assembled kit. But it will not
turn out to be $130 for the whole system bottle included.
Also - decide if you need a solenoid or not.

Go with whatever company you are comfortable with. CO2 is not rocket
science and certainly is not as expensive as some online stores make
it - up to $300 for a kit including the bottle. :-)