Compared to the Sierra1s on stands the footprint isn't all that different, a bit deeper and taller for the 590s (and heavier and harder to move around
). In a larger room I just found the Sierra1s a bit weak, but they're awesome in my smallish bedroom (use the 170SEs for surrounds). The 580s are a smaller footprint and $740 the pair and with a sub would work very nicely I'd think....I use them as surrounds in my main room (530s for rear surrounds).
@KEW for some comments on his 580s.