Don't worry about spider mites. You can manage them by taking your plants into the shower and blasting them with water in the winter time. In spring and summer,take them outside and blast them with a hose and then let them spend the summer outdoors. If you still have problems with this method, add a little soap to the water to break the surface tension of the water so it can get into nooks and crannies better. My gardenias and pygmy date palm always get spider mites in the winter and that's how I handle things. Also, for the palm only, I keep the mite population down by vacuuming them off. I use the narrow nozzle and go along the back of the frond. These methods work well to keep things in check. Just remember, mites love dryness and hate water. Any they wash away quite easily. So go get yourself that banana plant and enjoy it.

The three favorite I actually have are sumatrana X gran nain, basjoo, and good old dwarf cavendish. I really like those sumatrana X gran nains the best though. They have the pretty colored leaves like the zebrina, but the big wide leaves like the dc. and they're supposed to have the good eating bananas too. The ones I've direct planted out in the garden two months ago are around 2.5 feet tall now. Here is a link that might be useful: sumatrana X gran nain cross babies

I have had a Dwarf now for a few years and I have had it in WI the whole time. to respond to jordanz questions. First for the winter keep it inside you really shouldn't need to upgrade the pot I have on that is almost three feet tall and it is in a 14" pot plus if you keep it in the same pot if it reaches its max capacity in the pot it won't overgrow your house! just because they are a dwarf they can still reach sizes up to 5 feet! I have 5 banana's and they range from sizes from 2 feet to about 4 and a half feet in height. For you second question, it is true that they are very heavy feeders. I feed mine twice a month but not heavy either time more like a moderate feeding and the plant will not start to produce fruit until it is fully matured. It can take up to two years if it is growing at a continuous rate. I have had fruit a few times from my dwarf. the fruit is only about 6 to 8 inches in length but it is neat to see them grow and I think makes them even more delicious when you can eat them. I hope it helps a little and if you have any other questions I can try to help the best I can. Good Luck

Brown on the leaves can be normal. The yellow spotty stuff may be spider mite damage. Stuff on soil looks like fungus, it's hard to see. Either repot with all new media, or you can try scooping out the affected area and use a fungicide. I use apple cider vinegar, 1 teaspoon per 16 ounces of water.