I can see why, having come from a P&S camera, you would be attracted to a superzoom but IMO it is less than optimal.
Your stated photographics intentions are for "Lanscape, Street, Museums and Tourist Attractions".
These require lenses at the shorter end of the scale and the A77 kit lens, 16-50mm is a good match for those aims and is a high quality lens.
The Tamron 17-50mm is an alternative but not first choice IMO.
Ok, there will be times when you find the need for a longer lens but, in the short term you could pick up a cheap Minolta/Sony in the 75-300mm range.
A good camera deserves a good lens.

Choosing between the SLT and NEX is less clear; for the style of photography you espouse, I don't think the NEX lack of fast AF will be a problem for you but there is a shortage of NEX lenses which does limit your options.
You also lose in body image stabilisation which may be a factor.
NEX has a slight advantage in IQ but I doubt you would notice.