I've upgraded all my baitcasting reels by putting in orange seal boca bearings, carbontex drags, adding custom parts like star drags etc... Al my reels are custom to my liking. I also "Super tune" them by polishing all the contact parts and gears. It's fun and rewarding once you complete a reel. Nothing like getting that reel back out on the water to test what you've done to it. You also start learning which parts to oil and which parts need grease.
It's not cheap though. I usually fork out about $100 - $150 in upgrades to my reels but like
I said it's my very own custom reel that's been super tuned.