Moving up from SLT-A55

I had an A55 which was stolen and I replaced it with an A57. The controls are similar although it does have dedicated ISO button. Image quality is definitely improved and is better at high ISO. I would say that although I'm not a very experienced photographer it seems to me that the lenses you are using are not fast lenses. For low light work you really need a lens that goes down to F2.0 or less. These tend to be prime lenses. I bought a Minolta 50mm 1.7 off ebay for about £50 and it's great in low light.