If your Bs are nicely shaped, definitely DO NOT get implants. Implants are great for boobs that don't have a nice shape or that can use "filling out." B cups don't have as much head-turning factor as larger boobs, but they stay nice for longer. Compare Bs to Ds and you'll see that most Bs after 30 years old sag less than larger, heavier boobs (depends on firmness to start with, which varies, and also if you've breastfed, which can reduce the firmness). And natural Bs with good shape outrank bigger fake ones in the look-and-feel department once your clothes are off.
If you DO get implants, make sure you talk to the doc about massaging them. Many implants need to be massaged quite strongly for a long time in order to prevent scar tissue from building up. This can change them from the texture of real boobs to the texture of a baseball stuck on your chest, i.e. like rocks. Also, look very hard for the absolutely best doctor you can. If your choice is $3,000 for a doctor in Lancaster or $8,000 for a doctor in Beverly Hills, that extra 5 grand will mostly likely be VERY well spent. But you have to look at their before/after photos and hopefully talk to women who've gone to them. Stop women who have great looking fake ones and ask who did them. Ask to look at them naked. You'd be surprised how many women who have nice fake boobs willingly show them to people, even to guys.
But like I said, if you've already got ones with great shape, DON'T DO IT!