You've got a lot of research to do. Read through these threads carefully because they are as real as it gets. Nobody here has an ax to grind with any one treatment method. You need to consult with doctors, family, friends, on the internet.... the works. In the end, only YOU have to feel good about your decision.
I can only speak for myself. And I emphasize that no two people are exactly the same. I was diagnosed at 56 and I too am sexually active, or I should I say was (temporarily). As I mulled over my treatment options I kept one thing foremost in my mind.... getting the cancer out of my body with the highest success rate possible that it would not come back. When I concluded that both radical prostatectomy (surgery) and radiation (either seed or regular) had equal success rates over 20 years I looked into things more closely. Every, and I mean EVERY physician I consulted told me, at the relatively young age of 56, to have the surgery to remove the prostate. The reasoning is that in our 50's, our estimated life-span is longer and with radiation, there is always a chance the cancer can come back over time and if it does, the treatment options available then are far more limited. For instance, after undergoing radiation, if the cancer comes back, I was told removal of the prostate is not a good, viable option. However, I was also told that once the prostate is removed, assuming the cancer has not escaped the organ, that's it, finito, sionara, adios............... there is simply no prostate for a cancer to take hold again.
Now, as for the sexually active part... that's another story. I was fairly to heavily active prior to the surgery. Both physically and psychologically, I am currently inactive. While I can get a partial erection using Viagra my sex drive is currently down. I have no permanent partner, so this makes it worse. Mind you, I am less than two months from the surgery, but I miss the good ole' days. Part of my problem is that while I was recovering from surgery, one of my best friends died, and I am left feeling down most of the time.... depression. For that, I will continue to seek counseling and take Prozac. But I miss the sexual urge and a good stiff erection. My doctor told me that will come back with time and he counseled me to be patient.
MGL, good luck. You have this board to help you do your research. I had the surgery done with the robotic DaVinci. If you decide to go that route it will cut down considerably on your down-time and you'll be back to a relatively normal life again in 30 days. If you go the open surgical route, the recovery time, as I understand it, will be closer to 60 days.
As for me, I chose the surgical route because my Gleason's were 3+3=6 and 3+4=7, and I was not going to be looking over my shoulder the rest of my life faced with any chance that the cancer could come back. Prostate cancer, while very slow-growing and curable in its early stages, is not a pretty way to go out if it spreads outside of the gland.