I would keep the new cat/kitten in a separate room with a door and allow
 Barney to get used to its presence in your home.  If you have a door
or window screen, you can open the door and place the screen across the
opening and see how they behave in sight of each other.  Another idea is
rubbing a towel on Barney, then rubbing the towel with Barney's scent on
the new cat.  After a few days, you can put them in the same room and
see how they get along together.

We have been feeding an outside brown and white male tabby (Buster
Brown)that sometimes comes into contact with our indoor/outdoor cat,
Moo.  Moo is a large fixed male, a black/white Norwegian forest cat mix,
a gentle giant, who likes to hunt, but runs away from Buster Brown.
Today Moo was sniffing and eating some of Buster's food in the backyard,
 when Buster appeared, chasing Moo away.  They seem to coexist with no
problems or fights.

Our two indoor female cats seem to really like Moo, and they sniff each
other through the screen door.  The screen door seems to be a big help
in getting the cats adjusted to each other.

I don't think it matters if you get male or female cats.  Sometimes
female cats hiss, fight, and are more aggressive than males.  I've never
heard Buster Brown or Moo hiss or fight with each other.  One of my
friends took in a female cat for a while, and her male cat took an
instant liking to her, as he was constantly grooming the new female cat.

I would get a youngish, playful female.
I've always introduced all pets without separating them for long.
But I was around in case I had to interfere. I let the pets look and sniff
at each other.
Usually then the new cat goes into hiding for up to 24 hours.
I put food and water under the sofa where the cat is, talk gently to it and
place a litter box nearby.
I close the door and leave the cat alone until it comes out of hiding by
itself.
It's also important that it can investigate the whole new place when the
other cat is not around.

Pick the cat on a Friday if you can, so that you can be around during the
weekend.
Close the door of the new cat's room while you're away until you're sure
that they get on well.

Make sure that each cat has it's own food bowl and litter box.

Good luck.

carola