Both stages are built to last and are very dependable. That said, there are other second stages that perform better. There is no reason at all that you can not mix and match a Conshelf first stage with any second stage (with a rare few exceptions). My wife is diving a Conshelf first with Scubapro seconds.....I don't think I have one reg that is not a mix of some kind. A combo like a Conshelf first and octo with a much higher performing primary second would IMO be a great setup. A dependable rock solid first and octo with a great performing main second stage sounds like a great way to go. The biggest problem is finding a high performance second by itself, although they do show up on Ebay from time to time. Something to keep in mind, 99% of the performance of a reg is determined by the second stage. As long at the first delivers enough air volume at the correct IP the second stage does not "care" where the air is coming from. The Conshelf first will do that dependably. If you want to stay with solid, dependable metal stages a great second stage to consider is a Scubapro 109 that has been converted to a balanced version. A well tested design, very common on the used (Ebay) market, parts are vailable and performs close to the best of them. Non balanced 109s are very common and the conversion is simple.