I'm an ass man myself. A nice firm, tight ass and a tight stomach trumps everything in my book.
As for breasts, something around a 34B - 36C range would be my ideal for natural breasts. I will admit that on the right girl, a fake D can stir up quite the bloodflow for me somewhere..
But as you can tell - every guy is different. You're also asking on a bodybuilding forum, so the opinions may be skewed. (Ask what the ideal weight for a male is on this board, then ask a different demographic the same question - you'll probably get 2 very different answers). Also being "fitness" centric kind of guys, we may favor athletic leaness over other things...at least I do.
I'll be the first to say that breasts really don't matter that much, but honestly, all things being equal, the girl with the bigger, firmer breasts is going to have more of an affect on me whether I like it or not.
You should ask some girls that have had breast surgery done about their opinions on them. I'm guessing (and only guessing) that most will say that despite all that we are saying on this board, men do behave differenty around them now, and things have been much easier for them.
If you're looking to find that special someone, I don't think surgery is a wise choice at the moment. Purely guessing by your own "nice butt" comment, and thoughts of you doing BJJ, I don't imagine you'd have a hard time finding someone who is interested in you. If anything, once you find the "right" guy, you can "reward" him with the boob job afterwards, if you still feel that you want to do it for yourself. I just hope it would be first and foremost for yourself.
If you're just looking for some carefree fun while you can...I imagine that surgery would help with that.
I'm not a judgemental kind of person. Certain things are important to certain people, while not important to others. Who am I to judge other people? I haven't lived 1 day of their life, let alone a whole lifetime.
While obviously a different situation - it's still somewhat the same: I was quite the unconfident, skinny teenager. The thought of being a virgin for the rest of my life was a huge concern for me, among other things that weighed heavily in MY mind. (To people having it - sex is no big deal. To people with big boobs - they're no big deal. To people with money - money is no big deal, etc).
I went to the gym religiously and did things to improve my body. While purely superfiscial, as it was only body that changed, my own confidence increased. Not only that, but yes, the opposite sex acted differently towards me too. For me, I NEEDED that physical change in order to love myself, sad as that sounds. My life has been better ever since.
If this is something you NEED to help yourself, then I see no problem with it. But considering the cost, it may not be the best choice. Throw a couple grand into your RRSP's (or whatever the American version of a retirement savings plan is), then maybe splurge on some special clothes that you wouldn't have bought before...some sexy, attention getting clothes.
NOTE: if you're a model or an actress or in some kind of profession where your asthetic appearance is of higher importance, then I'd have to say go for it. A friend of mine was getting way less parts than me, then she got a boob-job. BAM! She's in the main cast of Falcon Beach. BAM! She does a Lion's Gate Film. BAM! She's flown out to Hollywood to do another feature film. Of course you have to have talent to go along with it, but every advantage counts in that business.