Play:3 adequate for TSF, or Play:5?

Already have Play:3 within the space in question, just curious if Play:5 would be justifiable. In short, TSF is about 450 for the room, which is more a rectangle than a square. Dilemma (if you want to call it that) is I'd like to own the flagship Play:5 if for no other reason than to have the best technology available from Sonos, but not sure the room will be sufficient enough space for it. It's a lower level Michigan basement, where a Play:3 is presently on its own "room" assignment as a stand alone option. Currently, the sound is quite awesome but it does take the 3 being a little bit on the louder side to fill the space acoustically. I know a 5 would do that at low volume, but feel it's unlikely the 5 would ever be used in this space at anything beyond 1/3 its maximum output. As such, does it even make sense to entertain the 5? Does the lowest 1/3 of its capacity produce a different enough image than the 3 at moderate to mid-range? Would it make more sense to leave well enough alone, or potentially add a second 3 for a stereo pair?

A lot to discuss here, in terms of all available options. Please leave your opinion when time permits. Thanks, folks!