Larry's advice was excellent. Although poseidons are highly regarded and often considered to be among the best in regulators, the main problem associated with them is servicing them. I've been diving poseidons for years, but after my technician retired and i had no one to service them i got really frustrated and sold them. I bought some apeks atx200, and diverite rg2500, and am very happy with their performance and their ease of servicing. The parts for both apeks and diverite are half the cost of those for poseidon and also the accesories, such as long hoses are half the price too. In Europe poseidons are definately worth it, because of the support, but her in the US, it's a constant waste of time and money. I don't know much about oceanic, but i'm pretty sure that in parts and servicing you will save a load of money. If you want the quality of poseidon, go with the apeks line, their right up there too, and i've taken mine pretty deep and honestly can't tell the difference between poseidons and apeks. Haven't tried the xstream though....