A solo Oscar in a 75 would be a great wet pet. They are a ton of fun and very interactive.
As far as where to buy one, I'd say anywhere is fine, as long as you find one that is healthy and looks how you want it to. I bought all 3 of my O's at petsmart and they are all happy and healthy.
As far as 2 in a 125, I'd say that you'd be fine with that, maybe even add a few dithers.
When it comes to adding multiple to the 75 to grow them out and pick a favorite, that's up to you. I don't think I would do this myself, because if I had multiple Oscars I'd probably end up buying more tanks to make space for them (what I have now). Also, you'll probably have to end up just giving them away as most lfs don't buy back O's, they are just way to cheap as juveniles for them to worry about buying an adult from a customer.
Good luck with the tank and the new O. Keep us updated.
As far as where to buy one, I'd say anywhere is fine, as long as you find one that is healthy and looks how you want it to. I bought all 3 of my O's at petsmart and they are all happy and healthy.
As far as 2 in a 125, I'd say that you'd be fine with that, maybe even add a few dithers.
When it comes to adding multiple to the 75 to grow them out and pick a favorite, that's up to you. I don't think I would do this myself, because if I had multiple Oscars I'd probably end up buying more tanks to make space for them (what I have now). Also, you'll probably have to end up just giving them away as most lfs don't buy back O's, they are just way to cheap as juveniles for them to worry about buying an adult from a customer.
Good luck with the tank and the new O. Keep us updated.