I would make the same suggestion as Herman.
Putting a balanced 2nd stage on your existing 1st is the only significant upgrade you can make.
If you want to keep it all AquaLung then the LX or Legend second stage is the way to go......an Apeks second is another option......all 3 are an Apeks design and use the same service kit. AquaLung and Apeks are under the same parent company so most AquaLung dealers are also Apeks as well.
(all balanced second stages no matter if they're Apeks, AquaLung, HOG, Zeagle, Atomic or Scubapro will be indistinguishable in how they breathe)
As for the dealer, obviously they will prefer to sell you a brand new complete regulator but as long as they aren't actually giving you bad advice or false information they should be satisfied with fulfilling your service and training needs.
.....and no, it's not that uncommon to have a mixture of brands and ages of accessories on a 1st stage.
Putting a balanced 2nd stage on your existing 1st is the only significant upgrade you can make.
If you want to keep it all AquaLung then the LX or Legend second stage is the way to go......an Apeks second is another option......all 3 are an Apeks design and use the same service kit. AquaLung and Apeks are under the same parent company so most AquaLung dealers are also Apeks as well.
(all balanced second stages no matter if they're Apeks, AquaLung, HOG, Zeagle, Atomic or Scubapro will be indistinguishable in how they breathe)
As for the dealer, obviously they will prefer to sell you a brand new complete regulator but as long as they aren't actually giving you bad advice or false information they should be satisfied with fulfilling your service and training needs.
.....and no, it's not that uncommon to have a mixture of brands and ages of accessories on a 1st stage.