Sony a57 used with 15y/o Tamron 28-200

I cannot give you much advice regarding the lens you have but I recently bought my A57 with the 15-55 and 55-200 kit lens kit and the results so far have been fantastic. The camera itself is extremely good and takes great pictures, and I am really enjoying the myriad of setting I have at my disposal.

As for other lenses I have been looking at super zoom lenses for a 1 lens for all situations, mainly for traveling travelling, negating the need for multiple lenses and changing on the run (keeping dust out of the camera etc). You can pick up a new Sony Alpha 18-250 off fleabay for about $200 so might be within your budget.