GVC-border, your opening post amused me because I have exactly that: a wiry terrier mix (although his fur is soft despite looking wiry), and I have Boo who is no doubt some sort of poodlely mix.
I wouldn't have ever chosen those two small dogs in a shelter, but that would have been my mistake. They are wonderful dogs, and Digger has caused me to grow a strong appreciation of small terrier mixes, so I might have one again.
I will always be seriously dedicated to the border collie, and will always have one or preferably two of them. It is hard for me to imagine my deliberately choosing a different breed.
If I were to go out and deliberately choose another breed to have in addition, it would probably be a Malinois. I have thought about a Jack Russel but would be more likely to go for a mix, like Digger. Papillion is another I might choose. But I think that if I were to choose a small dog in the future it would be more likely to be a mix found in a shelter or rescue.
You never know, though.
Left to right: Kit, Jester, Boo, Digger
"You gonna throw that?" --Jester: 2001 - June 24 2016. Remembered with much love.
"I'm grouchier than you are" --Kit
"I love everyone!" -- Boo
(Boing! Boing! Boing!)--Digger
And not pictured, Benjamin the cat, who thinks he is a small border collie with superpowers.