How big is your room and what is your normal listening levels? For example a with the wharfedale evo2-40's you need about 64 watts to listen 12 ft away from the speaker at 92db {3db headroom}... They are 6 ohm so most AVR's will be fine with them, I have mine on an XPA 2 which is 300w per channel and 4 ohm stable , But NEVER use 1/10th of that...
I have to say I tried a lot of speakers and the Wharfedales impress me, they sound good with anything I play, I have them paired with subs, and crossed at 100, but I am very happy with them... I tryed some Kefs and a few others, and for the sale price they will be tough to beat, actually even at $2000 a pair they arent a bad choice {although for $2000 the ascend towers are attractive}, the sale just makes the evo's a no brainer..
Also with towers you get more cabinet area so normally more accuracy and clearity in the lower ranges... IMO most of the bookshelfs I have heard need subs for good music, but there are some very capable home theater bookshelfs out there...
I like the mids that towers produce vs the bookshelfs and smaller speakers {the ascend sierra and 340se's are both acceptions to this rule, pretty nice mids from both, a lot of depth}