Hi everyone,

I'm relatively new to the site but have been lurking for a month or two. This topic has been covered several times, but I hope someone can help provide some guidance...

I've been shooting with an A300 for the past 6 months and as of late I've started researching lens upgrades. So far I've picked up a KM 50mm 1.7 and a Beercan, both mint. They've been working great so far and I intend to continue with them moving forward. I may add a newer telezoom like the 70-300G, but for now I'm searching for the optimal "general purpose" lens to replace the kit 18-70. After reading just about everything out there on the available replacements, I've narrowed down the list to the following:

Tamron 17-50mm f/2.8
Sigma 18-50mm f2.8 (2nd gen)
Sony 16-105mm
Sony 16-80mm CZ

The list is in no particular order. It seems each of these lenses have received rave reviews, so other than trying to base the decision on cost, I'm having trouble deciding which way to go. The Tamron and Sigma are priced "right" and the optical quality is said to rival that of the more expensive Sony lenses. I suppose my only real concern with those is the focal length coverage - will I really miss the 20mm between those and the Beercan? Would I see an appreciable difference in quality going to either of the Sony lenses?

Thanks in advance!

Tom