No experience with the Von Schweikert, but have heard the 3.3's extensively in a good friends high-powered SS Levinson system. They have some of the deepest, cleanest bass I've ever heard in his configuration (or any other for that matter). Very dynamic, fast and detailed. I do believe they would need some muscle behind them. Very large, heavy and teutonic in appearence. Side firing woofers reqire some room to breath. Definitely a full range sound with nice balance...perhaps a bit heavy in the lows, but I'm just not used to hearing that kind of bass being a SET/tube guy.
Marco
Marco