Grizzly makes a decent dead center, IMO. I have one with a carbide point. It works great, and it didn't break the bank.
As for using dedicated TBC bushings vs. the ones that are for the kits, I use both.
I find that the TBC bushings sometimes fit tighter in the tubes. I really have to make sure that all excess glue (epoxy & ca in my instance) is out. I've also found that some of the TBC bushings are at different diameters than some of the kit bushings. Sometimes they are a little proud of the kit bushing, and sometimes a bit shy. In practice, I really haven't found this to be a problem.
As for turning, the TBC bushings fit deeper into the tubes, and I think this helps with stability. The stock bushings don't have a 60 degree bevel on them, so they tend to leave a mark on my dead center and live center. The dead center I'm not too worried about, as I have the one with the carbide tip. My live center will need replacement soon as the tip looks like it's been chewed up a bit from the bushings.
With either the stock bushings or dedicated TBC bushings, going TBC as much as possible has really helped with my pens. The headstock and tailstock on my lathe are off center from each other. I've done what I can to get them close. Height wise, they are fine, but front to back they are off a little bit. If my lathe were still under warranty, I'd take up the matter with the manufacturer.