It depends what you mean by "fast" and what you mean by "soft".
As a general rule, soft rubbers are not very fast. If you want a fast rubber, it should be hard.
Soft rubbers are faster than hard rubbers if you hit weakly. But if you are hitting with full strength, the hard rubbers will produce a faster shot.
You could try Skyline 3-60 and add some booster. Or add some booster to your Hurricane 3-50. Hurricane 8-80 is even softer than 3-50. Adding booster will make the sponge even softer.
You should try Friendship Battle 2. It's softer than Hurricane and has a tacky topsheet. Plus it's cheap.
Rakza Z is a decent choice. It's sticky and it's softer than Chinese rubber. It has a very high throw angle, though, whereas Chinese rubbers have a low throw angle.
Tibhar Hybrid K3 is a decent choice as well. It has a soft topsheet, but the sponge is pretty hard.
