I've sold A/V gear in both the Quad and modern surround ages. Here's my take:
1- Having identical speakers for the fronts and rears is imperative. Large fronts and small rears can be acceptable for movies. There is often very little rear signal in the rears on movie soundtracks. Often, it is only sound effects. 5.1/Quad usually has very active rear channels. Surround music sounds best with matched fronts and rears.
2- The center channel speaker is a difficult call. It is imperative that it be timbre matched to the front L & R. Identical L, R & center is most ideal. On my main system, I would love a matching Mission 775 tower. Because it would be near impossible to accommodate a tower below my 60" plasma, I had to settle for the matching center. Yes, this is a compromise. Placing the center vertically on either side of the screen, shifts the audio image, which can be maddening. Placing a vertical or tower speaker on its' side will also shift the image, albeit not as severely as placing it to the left or right of the screen.
3- The subwoofer should compliment the mains. There are three kinds of subs:
A- Bose - Sub is designed to do lower midrange and upper bass. This woofer is incompatible with most other speakers.
B- Sub/sat systems. These subs are generally a mismatch with any full-range or tower speaker. They are meant to augment small speakers, which have little or no bass.
C- Subwoofers as originally intended are meant to augment full range speakers. They aren't meant to create all the bass. Instead, they shore up the bass by augmenting the low end of the speakers' range. They also add subsonics, which you can't hear but can feel. Hence, the term SUBwoofer.
My recommendations for getting the most bang for your A/V buck:
1- Speakers offer the biggest performance increase and the most bang for your $$. More money here will yield the biggest leap in performance.
2- If you listen to a lot of vinyl, extra $$ spent on a phono cartridge will also yield a quantum leap in performance. The tonearm needs to be compatible with the cartridge. For 35 years, I've been listening to vinyl with a Moving Coil, which usually requires a transformer or pre-pre amplifier. Since most cutting heads, which etch out the grooves on master disc, are Moving Coil devices, MC cartridges most closely mirror them, and IMHO, are best at reproducing the subtle nuances.
IF you're looking for new speakers:
1- Audition them, preferably in a sound room (remember those?)
2- Although you're buying speakers for surround, audition the speakers in 2ch stereo. Retailers rarely have two pairs of any speaker set up in the same room. Auditioning in stereo also gives a clearer idea of how well the speakers image.
3- Bring CD's or vinyl you're familiar with.
4- On speakers you're seriously considering, make sure they're "toe'd in." Speakers operate like binoculars. The image becomes real when they are angled properly. Angling them slightly toward the center reveals how well they image.
4- Audition speakers with classical music, even if you listen to classical a small percentage of the time. It is acoustic music, rather than a sweetened electric/electronic studio creation. Soundstage, tonality, and imaging, or lack thereof, are revealed most clearly on classical music. If speakers sound good on classical, they will sound good on everything else, too. "Rock speakers" may sound great on rock, but could be a major disappointment for other types of music.
5- You can only compare speakers by A/B'ing them at the same time, with the same source material, through the same gear, in the same room. One's recollection of how speakers really sound lasts less than 90 seconds.
6- Bring them home and audition the speakers in your room. This is time consuming, and a pain to lug the speakers around. It is the best way to test the speakers. Most reputable A/V dealers regularly provide their clients with this option.
7- Remember the "wife factor." The footprint, size, shape and color are often more important to your better half. I had regularly designed custom A/V systems with sub/sat or in-wall speakers. The woman often comments, "you're not cluttering my room with all that gear!" To avoid sleeping on the patio, a workable compromise is often advised. "If Mama is not happy, NOBODY'S HAPPY!" Fortunately, this hasn't been a problem in my home.
You can even place the electronics behind a wooden door, in another room, or even in a closet. Since most electronics use IR (infrared remote), RF (radio frequency) remotes, sensors and repeaters can be added. The electronics then become invisible.
