I hate shops, particularly those that organise courses.
I did never think that a shop is the proper place to search for technical tuition on an activity which can be deadly.
So I buy online.
For normal stuff like fins, mask, wet suit, low cost computer, etc., Amazon is just fine, you find decent equipment from brands such as Cressi, Mares...
For more technical and critical equipment (regulator, BCD) I prefer specialised resellers of renowned experience.
Some have their own online web sites, some simply sell on Ebay.
For regulator my recommendation is to stay on brands which can be serviced from any skilled technician all around the world and for which service kits are available online in case you want to service yourself (which in my opinion is the only safe way).
So my first choice is Scubapro, the second is Mares, the third possibly Apeks.
I would avoid an Octopus, a crap and low performance second stage.
In case you need it, you want full performances ..
So two identical good second stages, balanced and with the knob for adjusting the tendency to free flow.