Thinking of Buying a Sigma 18-250mm lens?

I'm new to live music photography but at the moment i'm running with only a 50mm lens. I'm looking to pick up a zoom lens for a decent price, i saw this on ebay but i'm not sure as ill probably need something with a lower appature 2.8 but do you guys think this would do until i can afford something new?

Here's the link

http://www.ebay.com.au/...0726189251

OR should i hold out and look at getting something like this

http://www.ebay.com.au/...0844858590

The 70-200mm is a MUCH better choice. The 18-250 is weak at best and the extremely high f/ at the long end will render the zoom completely un-useable in the live music venues. At 6.3 you'd have to be in nearly full daylight to use it. You would max out your ISO and still be so underexposed you couldn't possibly save the image. We won't even go into how much noise would be present from being that underexposed.
You are looking at ISO 12800, f/2.8 and a shutter of about 1/250 in a darkened venue and that will be pushing it for exposure.