Hey man, you have to come to the realization that no one (or very few) keep the hairline that tey had when they were 16. It is a natural part of life. We all get older and we all die. Hair transplants are great for those who have lost significant hair (I had 5300 FU) but at your stage in the game - I am going to agree with the other posts. Take propecia and realize that everyone ages a little.
If you had a hair transplant now - you are just risking an unnatural look later. I don't think it is worth it at all. Wait a few more years, start propecia tomorrow and see how that works.
On the other hand, I know you just want to look your best. But let's face it - most guys do this hair thing because of the women. And I will tell you that most women (even the younger ones) are not going to blink at eye at your hair loss