I'm wondering about the container size too. If this plant is basically the property of your cat, I would not want the container to have too much exposed potting mix which the cat begins to use as an alternate litter box. If so, then large pebbles over the exposed surface would be called for. If your plant goes from a south facing balcony a few feet inside the window also facing south, little change of its environment, unless there is a heating vent blowing on it. I've never kept one indoors in a container, but grasses are pretty hardy plants and even look good planted in a bird bath to simulate a water feature....which requires regular watering. However, mine planted that way died, so I'm no help telling you how to keep one alive!

The jury's still out on the hardiness of Prince and Princess. Growers are conservatively listing as zone 8, but this will likely change with time. It is at least 1 zone hardier than Rubrum and feedback shows it to likely be 2 zones hardier...that would place it as a solid zone 8, possible zone 7, perhaps hardier. It does work well as a replacement for rubrum, which is not a reliable zone 8, particularly when a burgundy color is desired in a cooler southeast zone...and no, it's not the burgundy perennial grass the northeast has been after. It also can be a replacement for hard to get phormiums of the same color.

I love puple grass.

You might see if there are any wholesalers who can supply smaller tubes of the Purple fountain for landscapers - even if you ask a landscaper to buy them in - if you can get cheaper pots and sacrifice some plunes by giving a good haircut, you could try dividing the clumps & could probably produce 4 times the number for planting out. In terms of native grasses, I don;t know your area, I know I find a lot of roadside grasses in my area very pleasant even though some may be weeds. Do be careful though when I say "weeds" some species can be very invasive - Qld now has a problem with the other fountain grass. I found this site which can supply small trial quantities of seed and has some good sections of notes on grasses and their uses (no commercial interest) Here is a link that might be useful: native grass seed supplier