Hey Desacrator, I know we ask a lot of questions and push on certain subjects... that's because fish stores lie and misinform quite often. A lot of products claim to do things they simply cannot. There are a lot of myths surrounding aquarium keeping, and like mommytron statedm we just want you to have a happy, healthy tank.
I think Desacrator has said he wants to upgrade his tank size in the future. So I believe a slow-growing fish that will eventually get too big, is actually what he's looking for.
List 3:
3x Angelfish (maybe 4x) - increases your odds of getting 1m and 1f, just as long as you know to separate or return eventually! The different colors are all the same species, Pterophyllum Scalare. That means no matter how many colors you get, you'll still need to end up with 1m and 1f.
Hifin Pleco - good to be just one, this guy will eventually need an 80gal tank (once he is like 5 inches long, or so). If you don't want to upgrade, you can go with a Bristlenose Pleco that could stay in your 37gal forever.
Bala Shark - Shouldn't be a problem fighting with other fish, but will need at least 125gal (6 foot long tank).
2x Bolivian Rams: These are good fish, but if you can't find them and don't want to try online, you can also check out the festivum cichlid, and a few others that stay 4" or less.
2x clown loaches: I would really nix the clown loaches. Unless you get at least 5, who will need a 90gal (preferably 125gal) tank eventually, and want to keep them for 15+ years. They're a HUGE commitment.
2x Gourami: I would do either the gourami, OR the angelfish. Both are fairly temperamental, slow-moving, flashy fish that would probably clash. The angelfish are more "semi-aggressive" though.
If you want, we can provide you with a list of fish that would be comfortable permanently in your 37gal, and that would provide plenty of semi-aggressive, fast-moving fun.