HT = home theater, as in contrast to stereo music. Pretty much universally, if speakers are great at music reproduction, they'll also be great for home theater use. Unfortunately, the reverse is not necessarily true. Speakers with acceptable home theater performance could still have poor music performance.
It's best to have the left, center, and right from the same brand and series so they timbre match. Matching surrounds not as important, and matched sub not at all important.
I think if you get towers your mid-bass will be a little punchier. Kick drums will have a more visceral feel. But even if you get towers that have extremely low frequency response, you still ought to have a sub. The best placement of speakers in a room for proper imaging and sound stage is probably not the best place for bass response. Additionally, having an active subwoofer takes a significant amount of load off your receiver, as sub bass is the most demanding of power. But it is also possible to get a great blend between bookshelfs and sub. That's the setup I run, and it's amazeballs.
Good room correction is important for such a blend though, in my humble opinion. I'm not sure about the correction in your Sony receiver. Given that variable, I think your chance of satisfaction is higher if you get towers.
But don't get towers just for the sake of getting towers. If they hit fairly low but the mid range is muddy, you would've been better off with bookshelfs.
Just keep googling, and pay particular attention to the complaints more than the praise. On the other hand, you should also beware of morons using speakers improperly and blaming user error on the equipment.
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