Thanks Alcina... good advise.
[Self-hijack] btw, I took a look at that Sigma 17-70mm. Nice lens especially with the close focus ability. If I didn't already have the 18-50mm EX lens, I'd snap that up for the macro capability. The only downside is I would need an additional extension for either my dome or macro port to fit the sigma 17-70mm fully extended to 70mm to avoid hitting the glass... So I ended up leaving the store with a Canon 100mm macro lens... oh dear... now to get a port extension and diopter for it...