Congratulations on the new tank! And such a wonderful price too!
Don't buy bala sharks. They are an irresponsible choice of fish to put out by pet stores and distributors and get far too big for the vast majority of tanks when you combine the fact that they are fast-swimming schoolers with their actually physical size.
Dragon fish/Dragon eels are likely to be Polypterus
or brackish gobies. Both are inappropriate for the kind of tank you want to set up except under certain conditions, I believe.
Bolivian rams (one of my favorites
), corydoras, kuhli loaches, and dwarf gouramis are all fine in a tank that holds schooling fish as its "showpiece." You might want to think about pearl, moonlight, or snakeskin gouramis, however, as you will have the space and they may feel a little more comfortable with some dither fish. IMO
, a healthy pearl is much more attractive in a large tank than dwarves.
You could also go with just kuhlis or just corydoras. Having a pair each of a few different color varieties or species of corys would be nifty. I wouldn't get more than 2 pairs of Bolivian rams in that size tank, but that's just my preference.
Your sailfin pleco will be fine in there. If you're going to put your trio of brilliant rasboras in, why not get more? You could have a school of them and perhaps one of tetras or another kind of rasbora. Alternately you could move your rasboras out entirely and get a school of Congo tetras, which are truly stunning fish that are really underappreciated, IMO
. Just don't expect them to act as dithers for gouramis-- they're more likely to scare them.
EDIT: I also second the hatchetfish. :P