Advice for a quiet apartment: Boost speech but keep special effects & music damped?

If you're just looking for cleaner sound, you could just go with a pair of bookshelf speakers and an inexpensive stereo receiver. Bass is what travels through the walls, so as long as you don't use a sub you'd probably be fine.

If you want more of a "theater" experience, you could get a 5.0 system with a center channel and surrounds to go with the mains.

You could go with 2.0 or 2.1 and a phantom center if you want.

Have you looked at HTIB? Home Theatre In a Box.

You are looking for a compression technology which is known by various names in its various forms. The Audyssey version of it as implemented in my Denon receiver is called "Dynamic Volume". I can disable it, or set "day", "evening" or "midnight" for a progressively stronger and stronger effect.

Basically, this will boost soft sounds and/or cut loud sounds to a lesser or greater extent in order to achieve several goals. Primarily it's to stop you from having to ride the remote constantly because of low voices/loud effects. As a side effect, you can set up movies so that you can hear the voices clearly, but explosions will not wake people in the next apartment.

Your TV might have something of this sort built in already, that's the first place I'd look before spending money. I'm not saying that money spent on audio is a bad thing, but one shouldn't be forced into it.

http://usa.denon.com/us/product/pages/productdetail.aspx?catid=hometheatersystems(denonna)&catalog=denonna_us&pid=dht1513ba(denonna)
http://usa.denon.com/us/product/pages/productdetail.aspx?catid=hometheatersystems(denonna)&catalog=denonna_us&pid=dht591ba(denonna)

It's true that if you want to boost the dialogue above everything else, you'd need a center channel. However, with a quality set of speakers you wouldn't need to blast the volume for the dialogue to be clear.

Getting a pair of HSU HB-1 bookshelf speakers and a budget AVR like the Denon 1613 would be a great start to your system. If you like the sound and want to add to it later, you could buy a matching center and surrounds. If the walls are as thin as you say, I'm not sure a subwoofer would make your neighbors happy unless you turned the gain way down on the sub.

I would never recommend a soundbar unless there is something specific about your room that doesn't allow for placement of traditional speakers.

What are the dimensions of your room?

My (unintentional) experience with Dynamic Volume was a disaster. When I first set up my Denon 1612 in my secondary HT, it enabled Dynamic Volume by default. I was listening to some music, and the volume fluctuated wildly throughout the songs. I figured something had to be defective until I discovered Dynamic Volume was on. Perhaps others have had better experiences, but I stay far away from that feature now.

Oh dude, it is NOT for critical listening to music, lol. It's really good for movies, though, when the kids are asleep.

Yes, I never intended to use the feature. It may be great for movies, but this experience made me reluctant to try it.

I wouldn't want to fool around with dynamic volume for speech intelligibility, it compresses all the sounds together and might make the dialogue less coherent. When I am watching something and want to hear dialogue clearly but don't want to bother anyone nearby, I boost the center speaker way up, and turn the subwoofer channel way down. This really helps. You might just get a 3.0 or 3.1, and make sure you get a decent center speaker, this will help a lot I am sure.
Here is a setup that can get you there:
Yamaha RX-v373 $190
3 x Infinity Primus p153, $180
Dayton Audio SUB-1200, $130
Total right at $500.

For dialogue intelligibility, set up one of those p153 speakers as a center with the tweeter as close to ear level as possible. Aim the tweeter at position where your ears usually reside. Try to keep it upright, ie not laying on its side. Learn the features of the receiver, it should have a easily accessible way to get to the center channel level. Just raise the center channel level when you want to boost dialogue, but not much else. You'll want to turn down the sub or turn it off for this too. That ought to get you nice clear dialogue with everything else toned down.

I recommend getting a sub, because it would be better for speech intelligibility to not run the mains as 'large' and have them try to tackle the bass. The sub here is really secondary, but the one I recommended is supposedly very good for the price, and it will give you a fuller sound. I wanted to fit in a really good dedicated center speaker like this one, but prices have gone up on that model, and I just can not fit it in a 3.0 or 3.1 budget. Nonetheless, a p153 as a center will be worlds better than what you have now, especially if you set it up correctly. I think this setup would best any sound bar.

One more thing, if you can, try to give the center speaker some free space, so you don't want clutter around it or have it tucked in some kind of nook with a bunch of surfaces nearby. This will cause surface reflections which will interfere with the sound, thus lessening its coherence.

What I started with in my apartment and got no complaints from neighbors , and still enjoyed surround sound was the
-Polk RM6750 5.1 speaker set

For a receiver might want to look at
-Refurbished Denon AVR-1613

What I am willing to bet is your TV has only 2 speakers and the programs and movies you are watching are being given to your TV in 5.1 mode so all the sound meant for the center channel like the dialouge is missing.

A simple modern-day 5.1 receiver and even a pair of bookshelves running as phatom center will improve the sound

Maybe a step up yamaha, Harman/Kardon, Pioneer, Denon, Onkyo, whatever you can afford. If what you want is better dialogue intelligibility, an entry level receiver from any of these companies will more than suffice. The sub would be sorely missed from the sound though, these are bookshelf speakers and do not have strong or deep bass. Honestly I think you would be happier with a sub in the mix, even if it could only be played softly- bass adds a lot of depth to your soundstage.

Btw, refurbished electronics scares me. The last refurbished item I bought was a denon CD, player, it lasted a month.