I have a boob job, although i got mine before having kiddies ive had mine for about 3 years now and absolutly love them well worth the money that i spent.

Of course im no doctor here but going on personal opinion i would certainly wait untill you are at a happy and constant weight - massive weight gain and loss after could possibly make them 'sag' so to speak. Mine have gone a little flabby from the weight gain/loss whilst i was pregnant.

I myself am a 400cc which is about a large D sometimes DD on my body frame. As for the implants ontop of the muscle my opinion would be to ask about implants under the muscle, under the muscle gives a more natural look and will generally fall into the shape of a tear drop with no bra on. But again as i said im no doctor and im sure your dr has given you the ontop of muscle for a reason.

All i can say is you are extremly lucky to of found one that cheap Mine were about $14 000 including medications. You will also have to think about time you will be out of action the 1st week is very painful you will be bruised and bandaged for a couple of days. As for bra's etc. At about 1-2 weeks you will need to go back and see the surgeon he will then fit you with a special sports bra (not attractive at all) and you will wear that for a few weeks. After your dr is happy will your recovery he will then fit you and your on your way to buying new bras!!! YAY.
I havent had any back problems so i cant tell you much about that
Good luck with your decision. Do whats best for you! I love mine!!!