I have one of the new Poseidon rigs here and think it is great, you need to be running a higher I.P. with it... If you do not have a Poseidon first stage or an adjustable first then factor that cost in.
The AGA mask is the MK-20 in our military but really is great mask also. I would go with the demand as opposed to the positive pressure model. OTS was running a great deal at DEMA for a mask, surface breathing valve, buddy phone, and swivel connection combo (yup, I kicked myself last year for not picking some up also...)
Kirby Morgan has a great new mask called the M-48, the pod style mask. One of the most comfortable rigs I have used it can also be run with a re-breather... They also have a EXO-26 mask that now comes standard with a great balanced and adjustable regulator but it is much more heavy duty and better suited to surface supplied diving. Kind of a replacement to the Band-mask...
The Ocean Reef is an alright mask, it does not breath as easy or efficiently as the others listed. It is not as durably constructed in my opinion but is a little cheaper than the others usually. Consider how much diving you will do with it and what types of diving...
If your going to use the masks for any length of time then go with one of the others...
Look around for a deal on a used one first, AGA and Kirby Morgan EXO masks are usually around if you look.
Good luck in your search, try to find a place to test dive the mask prior to purchase and make sure it fits well...
Jeff Lane