I keep goldfish and can attest to higher water temps. Mine stay in 74* -78* water and LOVE it. They stay more active and digest better when the water is over 68*.
Having said that, I can tell you I have tried several times to plant their tank and it didn't work.
I have talked to other goldfish keepers that had planted tanks and got mixed reviews. It is possible but you have to keep them well fed. This means alot more PWC's though...alot more. A couple of the tanks affected the Goldfish negatively. They began to stress and bottom sit. This was attempted for a couple of weeks and they wre then pulled out of the tank. I would think it had something to do with water perimeters but really couldn't tell you one way or another.
So, it is going to be a hit-or-miss for you if you want to do it. It is doable but the tradeoff is more tank maintenance.
If you really want a planted tank, get a small 10 gallon and keep some cory's in there with them.This way you get to have the fun of the plants and the tank is small and easy to keep.
Here is a link to the my other favorite fish forum. These are mostly goldfish people so perhaps you can find what you are looking for there as well.
http://thegab.org/