I've a Canon EOS 450 and mainly use an old Sigma 18-200mm (f/3.5-6.3 DC OS) lens for general shooting, and it has to be said mostly the kids at sports events, or the odd airshow, day out. Nothing too specific. I'm pondering a new body but suspect I won't really see any big differences so had thought about a better lens, which may help. Looking at lenses the Canon L series seemed great until I saw the price, then I noted (ebay) these: Sigma EX 70-200mm F/2.8 APO HSM DG OS Lens Canon EF 70-300mm f/4-5.6 IS USM Not being hugely savvy, from what I read the f/2.8 compares with the canon's 300m - can that be right? What I'm really after is a better quality lens than the one I presently have and if possible additional zoom, for the sports matches. I know this will make decent photographers shake their heads in frustration - its too easy with DSLRs to ignore the basics and just crack on. So, any advice, gratefully received.