I haven't personally used watch4buy.com but I checked them out too and found out that,
1. Their website was registered on Aug 4, 2009 and will expire on Aug 4, 2010.
Generally, you'd want to deal with suppliers who have been online at least a couple of years. Genuine suppliers have usually been around for longer than a year and the expiry date for their domain should be at least a couple of years into the future (because obviously they want to hold onto it!).
2. They stock branded goods.
Most of the brand name items that come out of China are either replicas or fakes. We recommend that you assume that this is the case in the first instance. It's true that many high quality and authentic products are manufactured in China these days, but you do need to keep a close eye out because it's rather difficult to ascertain the authenticity of brand-name products offered by the Chinese. Even though the items are exactly the same, manufactured by the very same company as the authentic items, they can still be classed as fakes or unauthorized if the supplier does not have the distribution rights for it. In other words, if you buy a brand, you need the paperwork to support it.
3. Their contact emails are hosted on free accounts.
Of course, this is not a guaranteed way of telling whether a supplier is good or bad, but suppliers whose email address is at their own domain name are more likely to be legitimate than those using a free account.
Hope that helps. All the best!