Correct. No beryllium tweeters on the S-520s. Those things are expensive.
Usher don't try to do anything unimaginable with the bass response, which overall probably helps the speaker perform so well in the rest of the range it covers. Needless to say, to move lots of air, you need lots of cabinet space. And like you pointed out, adding a sub can take care of what might be missed in the LFE.

Many audiophiles not short of cash prefer stand-mounters (with or without sub's) over full range speakers simply because they often sound faster and more detailed with greater transient response.

Sig' begineth here: