Bolivian Ram OK for my tank?

I was in the LFS today trading in some extra guppies and saw these guys in a tank. They really caught my eye... the one fish really seemed to know that I was looking at him, because he looked right back at me. Every time I passed the tank he would come to the front of the tank and turn to face me, it was so cool. I asked the girl in the store what she thought about putting a pair of them in my tank and she said they were kind of agressive and needed a tank with other "bullys". I came home and did some research and it all seems to contradict what she told me.

Currently in my 55 gal I have 5 sunburst platies, 2 SAEs, 5 ottos, 2 ghost catfish (that NEVER come out of the bushes!!!), 2 yoyo loaches, 15 guppies (only 4 or 5 full-grown adults), and 6 khuli loaches. I also picked up 10 ghost shrimp today to help out with the little bit of algae I've got right now. I do religious water changes and the water quality in my tank is great.

I think my tank is pretty much stocked but I wanted to add just a couple of bigger/more colorful fish just to round it out. I was thinking of 3 or 4 threadfin rainbows, but when I saw the Bolivians today I just fell in love. A pair of them would look SO nice in my tank...

What do you guys think? Will the bolivians be ok in my tank or will they harass everyone? I'm not so worried about them eating guppy fry, that would be fine by me - those guys breed like gangbusters in my tank and I'm getting tired of chasing them around to trade them in or give them away.

If the Bolivians are no good for my community, would they do OK in a 10 gal tank with a few other semi-agressives? I'm currently in the middle of setting my 10 gal back up and want to stock it with only a few really nifty fish.