For me, the OCD-induced anxiety of having v3 and v4 in the same room would drive me to upgrade. Whether or not you would notice would depend on the source material. Some movies use the surrounds sparingly, for quick pans or bursts of sound. I've found that newer movies are using them more heavily, sometimes even for music (especially animated stuff).

Axiom M5HP VP160 M3 ADA1000
Anthem MRX 720
SVS SB-3000 (dual)