If you couldn't already tell (look at my avatar), I'm a goldie guy and not tropical at all. If you decide to go with a fancy, then you shouldn't need a heater. The recommended temperature range is anywhere from 52F to 72F, and can sustain higher and lower.
For example, I have an outdoor whiskey barrel pond with 2 red cap oranda's. They stay out all winter long (in New Mexico, drops to 20F on average with snow). The become more dormant during the winter, but perk back up in spring. I've had them wintered outside for 3 seasons now.
On the other extreme, the fish in my avatar (a Ryunkin) is living in 80-82F water, uncontrollably. The tank is upstairs and we can't seem to keep the temp down up here (even with the A/C). He acts just as well, if not better, than he did at the constant 72F water.
One thing about goldfish, however, is that they need good filtration, being one of the messier varieties of fish out there. The standard 8-10x turnover is alright.
HOB is best for the added aeration, though they can deal without much (reference my "pond", that is a 100% "natural" habitat. No filtration or aeration anymore).
What really draws me to the fancies is their attitude. They are the most "pet" style fish that I have ever seen. They remember you as well as feeding time (the actions you take associated... like turning on the light and lifting the hood). They will eat from your hand, let you pet them (no joke), and interact with each other, their environment, or themselves. They don't need companionship as a result. The Ryunkin inside explores his home each and every day. I change it up every week and he seems to love that.
Goldfish may need more care than standard tropical, but probably no more than your chichlids or of the likes. Plus, most of them are very beautiful in color (again, reference my avatar). For a 10
gal, I would go with nothing other than a fancy goldfish.
Just my opinions, and I hope you will consider them further.
