Hey Kiel, it's as much about room setup as it is the gear. The whole surround format is based around sound reaching the listener at a specific time from the different speakers in relationship to eachother. Here's some basics to help you.
The main listening position should be centered with the screen and the center channel. In your case, that would be the right seat of the couch from the screen view. It should be the tv is centered to the couch but that doesn't look possible in your case so we'll work around it. I'll add if i may that 14 feet is waaay to far a comfortable viewing distance for a 46" TV. 10' is about the maximum if you use the formula 2.5*diagonal=Viewing Distance.
OK, so the front three speakers should be matched where they have the same sound qualities or 'Timbre'. The purpose is for a smooth summing of the sound from all three front speakers which will be producing different content from eachother. They should be from the same manufacturer and series.
As for surrounds, no need to change anything-including the speakers. They'll do fine for surround duties.
Your budget leaves enough for a sub, so keep the one you have and get an additional sub. I'd use the Sony sub up front with the new speakers as a Mid Bass module, since it really isn't a sub, it just produces the low frequencies that the small speakers from the HTIB couldn't. That short wall on the left between the window and the back door should work for the new sub.
Lets look at placement of the front three.
Your soundstage is wide so keep it that way. It'll image better if the main left and right speakers have some distance between them.
The positioning is locked by the right speaker having to go to the right of the hallway doorway, so whatever that dimension is from the right of the screen, the left speaker should be the same. The distance to the listener is locked by the left speaker and the wall. Try and move it out from the wall about 6" and then align the right speaker the same by moving it forward to match the left. This will give you the triangle you want where the sound from the left and right reach the listener at the same time. Towers, or bookshelves, either will do. As stated inmy first reply make sure the tweeter height is about seated ear level, whic is usually between 36 and 40". Given your long viewing distance, you have a little rooom to play.
For your original Sony sub, Place it somewhere between the TV and the left side speaker, closer to the TV if possible. In regards to the center channel, because of the long viewing distance, the bigger the better. You can put it above the TV or below, just make sure it's angled properly to it's horizontal plane winds up at seated ear level again. Also most center channels are rear ported so if so make sure there's at least 6" behind the speaker for the port to breathe.
Let's look at some real world options for speakers. You've got a pretty big space so tower or floorstanders won't be out of scale and draw too much attention to themselves. Bookshelf speakers on stands are another fine option but you have doorways very close to their positions, so the risk of a knock-over is high...something to consider.
A good sounding, good looking option would be these.
http://www.bestpriceaudiovideo.com/catalog/16/7926/
It's narrow design heps with placement and the front firing port allows for the close placement to the rear wall and will reinforce bass extension and integrate better with a sub. For the price, it's about the best value out there.
An excellent matching center would be this
http://www.bestpriceaudiovideo.com/catalog/14/7929/
It's big, i know...but it's one of the very few center channels that by design, does things right. The two smaller midrange drivers will lock the sound and reduce what is called comb filtering. The added woofers will allow the midrange to play cleaner and sharpen vocal clarity. IMO it's one of the best center channels regardless of price.
Including shipping, we've spent about $500, so given your budget we've got about $300 left for a real subwoofer. Take a look
http://www.parts-express.com/pe/show...number=300-770
It's a kit, but all it requires to assemble is a screw driver and spray glue.Being carefull and patient, it should takeno more than half an hour..It's that simple! The 15" driver does well with the low frequency extension and it will pretty much crush any commercial sub in it's pricepoint. Read the reviews.
You'll want to use the crossover on the sub and set it between 60 and 80hz in combination with your existing Sony sub. Set your speakers to Small in the receiver set up menu and set the crossover freq to 100hz. That will send the the midbass to the Sony Sub which will 'roll off' naturally around 40hz. The new sub will start playing material around 60hz and lower to about 25Hz where natural room gain will take over.
Ok so that sums up what i would do with $800 and having to work with the same space without re-arranging the furniture and having to look at the gear day after day. Hope i've helped.
