well my time to reply since I'm gonna hit my second lvl 50 kin this week probaly 
first I like to react on something...
''
Fulcrum Shift provides one +25% damage buff per enemy affected by this power. In addition the user of this power radiates an AE buff that provides a +50% damage buff. Each target affected by Fulcrum Shift suffers a 25% reduction in his damage ''
It could be that I'm wrong but the odds where 40% and 20% before:/...maybe cause I always did the trollers version which gives only 75% of the original...
anyway..
Sonic is a great set for kinetics..+damage...and a huge kin -res from sonic..can't be better..
reason I would first use that cone (watch out with the knockback tho) and THEN use your cone sleep..
Fullcrum IS stackable yes..(the recharge and acc are awesome)..but since kins are best in big teams and damage caps are pretty much lower then first you should be able to reach the damage cap with 1 good fullcrum..otherwise you still got siphon power to back you up:P..
another idea for kinetics is
kin/elec (its better if you go the team kin way)..elec doesn't have that uber teh uber damage..BUT...short circuit (uber end drainer) +transference+fullcrum works great not to mention the long range nuke blast called thunderous blast..I like the combo since a good kin goes close to the mobs to fullcrum anyway..and the heal is high enough to restore if it doesn't work out perfectly..get acrobatics tho if you are gonna play that way
A speedster with sonic boom? Nice concept. I like heroes/villains with power choices based on concept rather than powerplay... and sometimes you might find out that your concept build works just nicely.
My kinetic Corruptor happened to get sonic attacks because I found some interesting chinese legends as I was looking for a good name. (I wildly mixed those for my background story. 
)
And one text was referring to Ying Long as "Echo Dragon", so I think I chose the obvious... 
If it has eyes, you can blind it, if it has blood, you can make it bleed, if it has a mouth, you can make it scream.
Wow. Sounds very cool. Thanks to all for answering, I've chosen sonic attacks in the first place for character consistency (a speedster making sonic booms) and it seems it was a good choice also game-wise. Cheers!