Bookshelf monitors are usually prized for their midrange timbre and accuracy. They obviously can't stack up to a floorstanding monitor in the bass department. That's due to a number of factors, and the drivers are only one of them. Cabinets are a big issue, and the bigger the cabinet, in general, if it's properly constructed, the bigger the bass. How do you think full range drivers ever even make it to market, and have some people swearing by them? Cabinet tricks help them alot, so they can go deep. Bookshelf speakers are usually more simple loads to drive- one crossover max usually. Floorstanding units usually have, by nature, more complex crossovers. More drivers usually equals more crossovers, particularly in models where individual drivers are assigned responsibility for reproducing different frequencies. That often results in a more difficult load to drive. SET amps don't usually do well with complex loads- they'll clip a lot faster with a complex load, speakers with multiple crossover networks that have varying impedence. Drives SET amps crazy. Conversely, couple a nice SET with a simple bookshelf monitor, and many will tell you that you're listening to midrange heaven. Matter of taste there. But what to do with the low frequencies? Well, particularly in a room of your size, 13 x 36 with an open end, with a lot of hard surfaces, you're going to run into crazy resonant frequencies and generally suffer in the bass department. So, you've got a bit of a conundrum. What to do? Go to gigantic floorstanders and just pound low frequencies, keep what you have and supplement with a sub, or even go to bookshelf for the best possible mid and high reproduction you can get, and then supplement with one or even two high quality subs to take care of the bass. Experimentation is the key. You need, again, to find what suits your tastes best. Raw power from your amp isn't everything. You'll need to consider speaker sensitivity, and monitors usually don't stack up with floorstanders in that department. That's a generalization, but it hold fairly true. In a space of that size, personally, I'd use at least one sub. You'll have to mess with positioning- corner setup usually gets the most out of a sub. Optimizing speaker placement will also help. You'll need to find the "sweet spot" or set up to create a sweet spot. It'll sound different in different listening positions, so you set your sweet spot where you want it. Ideally, you'd have to consider speaker placement- you can use the Cardas Golden Room formula as a starting point- choose what you want in a main speaker- accurate reproduction of mids (where the bulk of music is reproduced) and highs, or a big floorstander with thunderous bass- work in a sub or two, and then get some room treatments going to dampen some of the resonant frequencies you'll deal with in that room. Curtains, furniture, maybe a bookcase....the stone floors are probably pretty nice, and I doubt you'll want to cheapen the appearance with a carpet that may help deaden some of the character of that echo chamber. Rives Audio does room solutions, as do many other companies. May want to have a look there. Scroll some of the virtual systems, and see how people have used room treatments here on Agon to maximize both the sonic quality of their room, as well as making them look great. It's a big space you've got, and there are many ways to improve the sound besides just adding a sub.
