yes optimum bought ABB but it is still best to get ABB through a good distributor rather than Costello's (Optimum), plus the only thing left for retail from ABB is there line of drinks...
best thing for your gym to have is of course going to be impulse buy products and things that are ready to go... like the ABB line, myoplex RTD's Nitro-Tech RTD's, the new line of designer drinks sells well , and of course a wide selection of protein bars. these would be a good compliment to your gym and add a nice profit margin as well, as for opening a full line of supps in the store i have yet to see this work in my area or the surrounding areas but maybee thats because my prices are low and i have a good customer base. Again like i said before it depends on your surroundings and if you have any real competition, and dont think of GNC as competition, unless it is a well run FRANCHISED GNC and not a corporate run GNC. <----(investigate this)
But if your set on doing a full line of products i would go with :
Optimum powders
EAS
Muscletech
cytosport powders
cytodyne ( especially Xenadrine) this will outsell everything..
And of course what i previously mentioned above. I would even consider selling alot of the more popular MRP's in singles to up your margin even more and increase impulse buyers to try things, then move onto buying them in bulk....
And maybee some pro-hormones , depending again on what type of gym it is.. basically your best bet at first will be to stick with the basic larger more ADVERTISED products and adjust from there.
And remember as im sure you already know, MOST people at the gym are trying to loose fat, so have a wide selection of products that compliment that....