No ordinary person will get "custom" bearings. There are tons of aftermarket bearings though. In most cases, unless the bearing is shot, an aftermarket, even one with higher specs, isn't going to improve your casts. Here's what I think is funny....guys put high spec bearings into their reels. And then cinch the spool tension down. What was the point?

There are some other considerations....ceramics can run dry, sometimes are better in freezing conditions, saltwater applications, etc., but for the most part, stick with stock if nothing is broken.

In the case of Revos, I've found they respond REALLY well to removing the crap silicone based lubes, and set up with light oil and lithium grease.

x2 on the Revos responding to a proper cleaning and lube

X3, big time.  Many reels, including Abu Revos are severely over-lubed right out of the package.  After a good bearing cleaning with lighter fluid and a lube with 1 drop of Hot Sauce, you'll swear those bearings ARE upgrades.

Here's a thread I made that pertains to this. I don't bother to actually remove the pin so that I can take the spool bearing off, I just dunk the whole spool in lighter fluid.

http://www.bassresource.com/bass_fishing_forums/YaBB.pl?num=1277522242

That's why there are pros that do this.....it just isn't practical for the average guy. There are several advantages to grease. 1. Quiet. 2. Smooth. 3. Knobs and handles don't spin free on feel baits, transmitting false vibrations. 4. Heat can be an issue, especially with bigger fish, and light line. 5. Keeps liquid contaminants out.

X 1000 Drop your reel in the water for a period of time. Easier fix with greased bearings. Way better app. for Salt Water reels. Except spool bearings.