You're missing out by not coming to the island

Here's why....
1. The Fleet Arcade. US mags and books at US cover prices.
2. Well, you're not missing out here. There's a bunch of good pharmacies in Kowloon. Find a fairly big one and they'll be happy to take care of you. There are quite a few in TST, too. My parents aren't in town, so I can't ask em for a recommendation. Sorry! I'll tell you this, though. Shop around a little...you might be able to find a bargain.
3. The GNC store is near the entrance for the KCR trains towards LoWu. You have to go past the turnstiles to where the money changing place is. You'd get a better deal (and better stuff) at Nature's Village, though. Just don't buy the ProLab crap. I personally get all of my protein shipped from the US. I recommend Dymatize. It has digestive enzymes in it, and it even tastes good! No bloat or upset stomach.
4. XL stuff is relatively easy to get. If you wanna save some money, check out Bossini. There are good deals to be had in Wanchai and on Granville Road. Fa Yuen Street has good deals too. I haven't had a chance to check out Sham Shui Po yet though. Haven't been there in a few years...