The added bass extension of towers will allow you to cross over lower to the sub, but if your receiver only has one global setting, then you still have to go by the speaker that has the highest cutoff. IMO a good bookshelf blended properly with a sub is every bit as good as a floorstander. For music (with no sub) I prefer a good floorstander, but for HT, it's almost a wash when using a sub. What you should consider is, if you need stands too, will stands + bookshelf speakers cost as much as the floorstander? In my case, that answer was no, but in many cases it may be very close.