$1500 is that US or what as I see you are in Germany. That is not a lot for a decent 5.1.2 system especially to partner a Denon X4500 avr which is a good mid range avr, it deserves a bit more $ to be honest.
To get what I would consider to be a decent match for the avr and if you are in Germany XTZ do a range of speakers called the spirit range and are well thought of but excellent value for money.
You could get a pair of Spirit 4 for L&R with a spirit 6 for centre @ 835 euro, for surrounds a pair of spirit 2 for 390 euro or better still another pair of spirit 4 for 450 euro.
For subwoofer a 12.17 edge at 690 euro although they do other subs at around 500 euro but the 12.17 edge gives best bang for buck.
The new series Spirit from XTZ. Perfect for both home cinema and for hifi. Precise, natural and engaging sound.
www.xtzsound.eu
www.xtzsound.eu
XTZ does a 30 day buy and try so if you did not like them you could always send them back. Also for a full system they will do deals so worth contacting them for their best price.
For the Atmos pair depends if you want to use heights or upfiring. For heights another pair of Spirit 2 mounted high on the front wall pointing towards listening position would do fine.
That gets you a 5.1 system you could add something else for atmos speakers
