the thing is... there is no science to determine what the optimum temp is for living soils in indoor environments... so anything anyone tells you is just based on nothing but their own experiences. you could try putting some seedling heat mats under your containers to try and warm up the soil a bit... but honestly I think 65 is a fine temperature. If you look at soil temperatures in the natural world... they are just as low as your pots. the only portion that warms significantly is the surface (especially when exposed to sunlight). I would be willing to bet that soil temps of mid latitude environments between 4 and 24 inches (of depth) rarely exceed 70 deg unless their surfaces are directly exposed to sun. I would only be concerned if the temp dropped to like 55 or lower to significantly affect microbial or root processes. On an unrelated note... I know that 55 deg. is kinda the threshold value that we look for when hunting morels in the spring. once the soil temps get that warm, it's time to start looking.
most importantly, another way to look at it is like this... your soil temperature is going to select for microbes that are able to thrive and survive in your growing environment. Nature is all about selection. this is why it's important to inoculate your compost, whether it's outdoor or worm farm or whatever, with diverse communities of microorganisms so you have more chance at increasing the diversity of the community in your grow. This can be done by collecting bits of soil, plant debris, and fungi from your local environment because they are selected for by temperatures (among other factors) in your local area. It doesn't take much either... A tablespoon of soil from here, and one from over there, one from the forest, one from your garden, one from a natural field/grassland.... you get the point. Then when you introduce them to your growing environment through application of your compost (Elaine Ingham says this is the best way to introduce them) they will be chosen by natural selection for your environment.