U can try Front heights with your SVS ellevation ,mounting high on the front wall. Then u can place rear heights on the ceiling (above SL & SR ) tilted down towards the MLP. Denon X4500 will be better than SR6013 (specwise).
Based on my experience heights are secondary .The important factor in HT and to enjoy the same is to bring the Front Sound stage ,better bass management and integration of main speakers (bed layer speakers ) to the sub ,blended in a perfect way .I have heard many demos (both in showrooms & home demos ),the fact is most of people are not gifted to attain these factors (Especially in a living room its very hard to attain this.).Only very few demos are perfect which I have heard so far.