[anti]

sigma 75-300 or 70-300? you've mentioned both.
it sounds like the 70-300 (if this is the one http://www.ephotozine.com/equipment/tes ... est_id=369). it's a good lens but it's cheap, and the quality is reflective of its price. the lens is really soft in the 300 end but it does well with macro and what nots.

yeah all the numbers and codings get confusing, but it's basically referring to the grade of the lens. each company has their own specific brandings, like canon's L glass is the highest of the high and Sigma's EX is their best shit, so on and so forth. these forums have some good info http://www.fredmiranda.com/forum/ along with awesome reviews.