I have not heard SVS prime ellevation personally.Its having very good reviews globally. But here in our Country its price is very high when compared to abroad price (This is only -ve I feel).
The other option for heights can be Dali Alteco -C1 .I'm using it (Not saying because I'm owning it ).Its a good one for the price and its versatile one and have option for mounting as surrounds ,heights and on ceiling too (with an additional screw/nail) .U can able change the angle of firing by a switch on/off (if required ) provided by the manufacturer.
Between front heights and ceiling ,the best is ceiling mount for Atmos installation. In terms of Indian pricing Dali Alteco is approx 0.6x of SVS ellevation speaker price.
If u still want low price ,then sonodyne sonus 3540 can be checked ,which will be also can perform good to its price .(I was using this for past 2 years as Top Middle speakers for 5.2.2 Atmos earlier .Now Its been doing the duty of Voice Of GOD of my Auro3d 10.2 setup.
Do an audition possibly and select the speakers .