Welcome. It sounds like you're on the right track. That 5g hex isn't a bad setup. My wife has one that I bought for her for Christmas a few years back. Unfortunately, it does limit your stocking choices. She was getting antsy for more fish, so I offered to set up an extra 20H I have lying around for her if I can have the 5g for an RCS tank. Start taking your wife to the LFS
. She'll probably find some pretty fish that she wants, but you can't have because the tank is too small. Tell her she can have it if you get a bigger tank.