You can't mix ECC and non-ECC so I would stick with ECC if you want to use your current modules. I would also stick with 1066MHz because if you mix 1333MHz with 1066MHz, the higher clocked modules will be underclocked and in real life the bump in RAM speed doesn't offer anything. If 1333MHz is the same price, then go ahead and get it.
I would buy from whichever is the cheapest (among these known, reliable brands). Check TransIntl, they may be a bit cheaper.