Like they said, PetCo has been including their 40br tanks in their dollar/gal sale lately. They used to not do it, but apparently they've made a change. $40 is way better than $125.
If you do have to pay full price, I would look into a custom 40g tank made with similar dimensions, but rimless or with a starphire front. I have no idea how much more it would cost, but it may be worth it. I've noticed that there are some issues looking through the tank up close. The refraction can be a little tough on the eyes. I don't regret my tank, but I'd be a lot happier with it if I paid $40.
As far as where to start with a 40 br and sump, look for my build thread and Roman's (happysac) too. We both have a little different approach to what you're wanting to do. I have a thread in this COMAS sub group and one in RC's General sub group. Feel free to PM me with questions, thoughts and musings