I'm a little outa touch as far as big screens go, but for sound systems I can offer some advice.
I used to manage a high end stereo shop so there's several choices you can make.

Most consumers tend to go for the midrange, (although they think it's high end) sound systems. Like a Yamaha all in one system with surround and a subwoofer.

If you have the money... go for separate components.
For instance get a decent amp (I'm talking the stuff you see in high end audio magazines). Get a separate surround sound decoder.
You'll need decent left and right speakers as well as a center speaker.
Go for the high end stuff like Polk Audio or better.
Rear speakers, same deal.
For the sub, get something built for the job and use a separate power amp to run it. In fact if you can afford it, get separate power amps for all your speakers.
Use high end speaker wire (for gods sake don't use 18 guage or 12 guage or ..arghh. lamp cord) Keep the leads as short as possible and use directional wire. Use high end RCA cords from monster cable. Use proper speaker stands that isolate the base from the floor. Use monster cable T3 1/2" cables that have been properly mounted and be sure to get everything in phase.
Use a test tone CD to tweak the system so you don't get any standing waves or problems from bouncing sounds from walls cancelling things out.

Of course all this stuff costs big $$ so most people end up getting a cruddy Pioneer surround sound system, a cheap woofer and wire everything with 12 guage and then tell all their friends how great their system is.
(but guys like me who know better go into their houses and pretend that it actually sounds good)

Best bet is read up on some high end audio magazines and then go into a high end shop and deal with somebody who isn't pushing old stock or whatever he has in the back room.

To test out the stereo and bass response of the system use Slave to the Rhythm by Grace Jones. (take the speaker grill off the speaker and check the woofer on song #2. If it craps out, get a new speaker)

Basically, in the long run you can go for mass consumer oriented stuff like Technics, Pioneer etc... But you're much better off buying separate components from higher end companies. Even Luxman, Denon, Polk Audio, Monster Cable etc... will give you a high end sound that blows away the medium stuff like what you get from Future Shop.
Go to a high end shop. Even if you get the cheapest they've got, you're still gonna get a better sound than an all in one system from a mass consumer store. (and don't skimp on the rca and speaker wire)

btw: beware of the bait and switch crap and the "we don't have it in stock right now. Some stores like Liptons Electronics in Newmarket will sell you a stereo and then tell you to go get a coffee while they do the paperwork.
Meanwhile, they pack up the scratched up floor model while you aren't looking.
A telltale sign that you're buying a repacked model is to check the bottom of the carton. Audio stores open component boxes from the bottom.
Later, when you buy it, they re-seal the demo unit and seal the bottom of the box with packing tape. They drag it around on the floor to make it look dirty so it doesn't look new.
Always check the bottom of the box to be sure the packaging is original and when you open a new item, double check for price stickers or left over glue.
Or badly repacked components. It usually means its been sitting on the display floor for 6 months.

Also, don't let the store install your stereo for you.
Any scratched units like cassette decks that have scratches on top and quickly hidden inside the rest of your unit so you don't notice the scratches.
They'll also use the cheapest used cables that have been lying around the store.
Always ask for brand new, packaged components and sealed rca cables.