I think you'll be very happy with the green neons. They aren't quite as colorful as the cardinals, but after you've had then a while they color up nicely and even get a small red underbelly similar to the cards.
As far as cories go, they are great fish, but don't count on them to eat green algae from the sand. In my humble experience, algae eaters don't really solve algae problems - only balancing the light, ferts, and healthy plant mass can suppress algae. If 50 umol of PAR is causing algae on the substrate, try dialing it down to 40 or shorten your photo period to 8 or 6 hours. Personally I am always quite surprised at how little light some of these plants need, even the high light ones.
Also, keep in mind that in a new tank with aquasoil it's normal to get some algae growth. Very frequent water changes (daily first week, every other day second week, and twice weekly for next two weeks) can help but the ammonia leeching from the AS is bound to cause some algae to appear. Hopefully your plant growth will take over and suppress it.
Try using excel or glutaraldehyde daily to suppress the algae. It's a good supplement in case CO2 is not circulating throughout your entire tank.
Looking forward to new pics.
“We don't stop playing because we grow old; we grow old because we stop playing.” - George Bernard Shaw