Yep I second bloodfins and in the future would like to get a tank with maybe dark plants, dark gravel, and then a big ol' school of them.
I guess I've never been a huge fan of rummy noses because of their look. They just look so interesting that it's almost fake to me... something about their black and white tail where no other fish I've seen has it that irks me but haha, that's just me of course.
For the threadfins that you said are your LFS and are just silver, maybe it's the lighting or they're mostly female in there. If you look for males, they should have more reddish/green accents on their long top and bottom fins. Not to say the females are bad looking, but compared to the males they look really plane and aren't what we think of when we hear threadfin rainbow fish. They also don't grow that large so that wouldn't be a problem... some rainbow fish can be large but just like rasboras/tetras there are other variations that remain small. Threadfins are definitely schoolers but if they're really comfortable and the males are displaying to the females then they will be a lot looser and not schooling as much (but this is a good thing because when they display it's pretty awesome to see). their color improves as well when they're comfortable so that could be why they aren't that bright in the LFS.
Unfortunately I couldn't find much info on the Pseudomugil gertrudae ARU II that you posted - here's a profile on the version I's of the gertrudes that are a little different but probably behave similar to II. http://www.seriouslyfish.com/profile.php?id=223
Watching some other videos of the gertrudes I think they behave similar to threadfins where they will school if not comfortable but once comfortable they show off and display and play with each other http://www.youtube.com/watch?v=6UwR2kzdf-k
- so even though they don't school as tightly as tetras, they have an ace up their sleeve when they show off.