Yes, it was The Wet Spot that I got the zebra loach (it's actually a golden zebra loach, they had no regulars except in their gorgeous display tank which is, of course, not for sale) and they told me to check back in a few days. I actually work at another LFS but I'm not comfortable with the cardinals they keep so I shop elsewhere haha
As for the other suggestions, I'm looking for more color and did think about Rummy Nose Tetras, but worry that they will fade into all the green in my tank...not your experience? I'm not a fan of harlequins (just personal taste really) or blood fins, although they would probably do well. As for Diamond tetras I've heard they can be a bit aggressive. Diamond Head Neons are definitely pretty but pale in comparison to Cardinals IMO.
Decided not to go with Congos or a Betta. I've been planning this tank out for a while and have been suggested mostly to either go with Rummy's or Cardinals for the most part. Thanks everyone for your opinion!