We Sons Of Daley [Manhattan Blues]

Would there happen to be a Discipline or Power that amplifies or enhances Ki use?

Not directly, no. Certain powers go well together, but nothing directly impacts how you use your ki, just like none of it directly impacts your ability to CAST MAGIC. For instance:
--PK Armor would make you a lot harder to damage.
-- A PSYCHOKINETIC TRAP can hold someone helpless for a crucial moment while you belt them.
-- MOTION DETECTION (a PK power) is an extra layer of detection against sneaky people who think they can get by just on Ki Concealment.
-- PSYCHOKINETIC IMPACT can thump someone, emulating a DISTANCE ATTACK TECHNIQUE.
-- SHATTER, a PK power, can look remarkably like DESTRUCTION BY KI if you do it right.
-- FREEZE is a slightly weaker, single-target version of EVERLASTING MOMENT. Done right, it could be an ADDED STATE technique, like the FIVE-FOLD PRESSURE technique JOLSON has.
-- CRYSTALLIZE not only inflicts a penalty on an opponent, but also renders them vulnerable to MASSIVE DAMAGE aside from simple LIFE LOSS- things like BREAKAGE and AMPUTATION.
-- ELIMINATING SENSES (in Empathy) can render an opponent BLIND. At the right moment, this is devastating.
-- DESTROY FEELINGS (Another Empathy Power) can turn an opponent into a vegetable.

These are all abilities you have access to already. With physical increase:
-- Increasing your REACTION TIME is a simple task.
-- As is increasing your REGENERATION to the point where your wounds knit before your eyes.
-- TOTAL INCREASE can be layered with the rest and make you a bit of a powerhouse.
-- FAST MOTION is a hallmark of Ki users in particular, and you can EMULATE it with the INCREASE MOTION power.

There are a few others in various other Disciplines:
-- TELEPATHY would let you read someone's mind, which will give you a moderate bonus to all actions against them.
-- Later on in PYROKINESIS, CONSUME would act as an improved SHATTER.
-- ENERGY OBJECT CREATION (in ENERGY) can serve to improve your PROJECTION and act as another blind.

Also, point of curiosity -- what Discipline does Hide Matrix fall under?

It's one of four powers that psychics get access to for free. The other three are the ability to Sense Matrices, the ability to Destroy Matrices, and the ability to link a bunch of psychics together.