As you may have noticed I am a jerk when it comes to trying different systems, watching me figure out placement will make you sick... and I have a 12 x10 room full of speakers that have been setup and then replaced, my bookshelf collection contains 16 pairs of bookshelfs I put back in their boxes, not counting the 8 sets I have hooked up presently between my house and the office....
SO back to the OP...
I hooked my entire system in, the dual subs {wharfedale sw's}, the dac {at the time is was the xda1 since swapped out for the 2}, crossovers {around 90hz}, amp {xpa2}, and hooked in my source {laptop}.
I have a set of evo2-40s and a set of evo2-10's pretty much the same speakers except one is a tower the other is a bookshelf {I also tried 4 other sets of bookshelfs at the same time, this testing took me 5 hours of listening, some may remember my shoulder surgery and having a lot of free time on my hands, coupled with a mild depression from watching my years of weight training being soaked from my arm day after day and the constant searing pain from having a 30lb arm hanging from my severely damaged posterior, anterior, and lateral deltoid fibers}.
ANYWAY... I was very curios as to how the 10's compared to the 40's SO I tired this every which way, I played the 40's full range and crossed as I did the 10's, the 08's and a few others {including my tads that were new at the time}...
The results were........ The 40's sounded better full range, the 10's sounded better with the subs, so its pretty simple if you have access to subs, use them with bookshelfs {especially if you like bass heavy music}, I left the evo2-40s in that room for the simple reason they look better, lol and I wanted towers in there, I will sometimes shut the subs and run the mfull range, but I love how the subs sound, its a shame them subs don't get the attention they deserve they sound wonderful, not a ton of output for movies but a very nice sounding sub {I own 4 of them, lol}, they aren't popular in the US and probably because they were seling for $2100 each, which is silly... But fit and finish is first rate, sound is great, super fast, accurate, just really nice subs...
So in closing, the bookshelfs sound better with mids and highs, and the subs sound better with the lows, you put them together and you get a better experience...
here's a pic I took way back then I snapped when trying them out, the evo8s are on the stands the 10s are on the subs and the 40s are obviously the towers... The wharfedales are an overlooked powerhouse in the US, they can be costly but I have never seen a bad product from them, even their entry level diamonds surpass about everything you can hear in Best buy and aren't very expensive, very warm sounding lineups...
heres a pic of some testing I was doing when moving the jade 5's around before I bought the sb12's in paino
I ended up with the csb1 and sb12's in that room and moved the jade 5's and wd subs to another spot in the house...
I have had "serious" audio "guys" listen to the sb12 csb1 setup and the EVERYONE is surprised by the sound stage and quality this cheap system produces, for a couple thousand bucks, a pre, dual mono blocks, subs, and bookshelfs that sound better than towers costing $10K... Granted the csb1's aren't the end all to all speakers, but for the price they are amazing, and when setup correctly they do a few things very very well, I like all the music I have played through them to date, and I have gotten pm's from 5 different people saying they bought them after reading that me and J liked them and were very very happy with them....
But thats it, I haven't really bought a tower since I tried figured this out, and the only towers I currently have hooked up are the 40's and the lores, all of my other systems are built around bookshelfs.... I'll probably never buy a tower again and I have a long list of books I want, philharmonitors, WOW1's, Seirra 2's, PSB inis, PSB imagine b's, Synchrony B Ones, mmg's, ls50's, Aon's ect.... Now I could never own all of them speakers in towers, I would need another house to fit them all in, and they would be a pain to change out...