In all honesty, if it has to be a "cube", who cares.
When a driver has to be that small, it simply cannot reproduce an important part of the very discernible frequency range.
I bet that a 3.5" driver cannot even properly reproduce the fundamental of my normal speaking voice, and I'm just of average stature. My guess as to my speaking voice is 100hz, as that is a little over the lowest note I can sing, and I'm guessing that I speak at the lower part of my relatively limited vocal range (A bit more than 1.5 octave, not including falsetto). Heck, I'm pretty sure I've read that a larger driver at 4" can only go down to 120hz, so I'm afraid to ask what a 3.5" driver is really capable of.
Seriously, I'd just use the TV speakers for the aesthetics. The audio compromise won't be too great I think, comparatively.
And I enjoy and own PSB speakers too.