So, in Your Opinion...

Well, I've been looking around quite a bit to find a good CO2 regulator for my nanos, but I've been finding some rather mixed and contrasting results as to the members' opinions about each. Thus far, I have found the following regulators that use cartridges (a necessity, as I have limited space):

RedSea CO2 system
ADA CO2 (can I just use the basic $80+ setup, or do I have to purchase the 200+ "Advanced" set?)
Hagen Advanced System
Rex's Adapter
Nutrafin Adapter

Out of the following, does anyone have experience, and do you regret your purchase at all? I really appreciate any input here, as I'd rather take my time and go with the better system, instead of buying based on the cheapest prices... So, if any of you has any pertinant info, I'd really appreciate it.