There once were two cats from Kilkenny
who each thought there one cat too many
so they fought and they fit
they scratched and they bit
until instead of two cats, there weren't any
I gotta say I'm mighty proud of Buddha and Dasher. Since our return from Dragon*Con (five days in which the two of them had only each other through a closed door for company), we have been letting Dasher out with increasing frequency and, with the exception of one big fight which I stopped by letting loose with the full power of my voice-coached operatic baritone , they've been getting along pretty well. This mighty roar rattled the both of them to the core, which is not something I enjoy doing, but was a carefully-considered "surgical strike," as it were. 
And it seems to have worked. While there have been a few dust-ups, most of their interactions have been more of tentative peace gestures ... getting within sniffing range, walking tentatively around each other, even both kitty-loafing casually in the same room. It's still not quite "two cats, one family," but it's a lot more peaceful than I ever expected and has given me fresh hope that the normalization of relations between these two is actually possible.
Of course, their personalities will never quite be in harmony ... Buddha is gentle and affectionate and likes to lie around on his back, while Dasher is a big dumb lug who pounces on everything that moves and several things that don't. But getting Buddha past the idea that Dasher is "an intruder" should go a long way to making him more comfortable around the big goofball.
 Most people probably don't know this about me, but were he still alive, I could give Robert Goulet a run for his money on a good day. When you have a barrel chest, speaking from the diaphragm makes you a living megaphone. So when the cats are having a fight three feet away, and I open both barrels with "Cut it OUT!!!" ... they notice.
 Buddha in particular was so discombobulated that he hid from me for about an hour, after which time he slunk back very apologetically and wanted to be held in my lap for comforting, poor little guy.