I'd budget for three speakers across the front, as for movies/tv the center channel is the one carrying the most information. One sub may suffice, particularly for one seat, but multiple subs help smooth response at multiple seats (sub frequencies work a bit differently in rooms, try
this article, as well as part 2).
The lowest end avrs like the S510BT I'd generally avoid personally but may work for you. Use the comparison tool on the Denon site to see just what the differences are on various models would be my suggestion.
For speakers in your neck of the woods I'd look at Wharfedale, think they have some speakers that will work with your budget. A few hundred doesn't buy a lot of sub, but check out XTZ and B&K Electric.