Lots of great ideas so far...
I would get some new coffee tables in a dark wood color. Say, like the Dolce collection at Target. It would go great with the dark red wall and has a very sexy, moody feeling. I'd get rid of all those bookcases and just buy one large, dark wood media cabinet for the TV and hide all those DVDs in it. make sure none of those are visible cause it's just to visually overwhelming.
For the fireplace, get rid of all the clutter and just put maybe 3 items on the mantle all of the same color (I vote for off-white so that it goes with the off-white walls and pulls things together). As for other decorative items and accessories, I'd also use other off-white items to kind of go with the off-white walls and to also brighten it up a bit. Maybe even get a different piece of art over the fireplace because it looks very dark and murky in the picture.
If you got a large (4 x 6 maybe?) rug to center in the living room, like where the couches and coffee tables are, that would be good too to give more structure to the room. I'd like something in dark brown and off-white (or black and off-white) with a geometric pattern for this room. The neutral, contrasting colors would be very grounding here and draw your eye right to the center.
Check these rugs out as examples:http://www.ikea.com/us/en/catalog/products/20112619http://www.worldmarket.com/Giraffe-Rug/lev/4/productId/6544/Ntt/rugs/Ntk/Def/Ntx/mode+matchallpartial/N/0/Nty/1/view/10000/index.pro
Definitely get rid of the clutter of all those lamps. I think it would also help brighten things up if you installed two wall sconce lighting fixtures above the mantle on each side. If you got a large media cabinet for the TV, maybe try two decorative floor lamps on each side of it, something like these: http://www.ikea.com/us/en/catalog/products/30124301
I'd also fix up your little office area quite a bit, as there's too much stuff going on over there!
I really like the red accent wall and your couches. I think you can pull it all together with the tan couches, neutral carpet, red wall and dark walnut furniture. You also need to fix the curtain situation (maybe some breezy cotton/linen off-white tab top curtains like these http://www.target.com/gp/detail.html/sr=/qid=/ref=br_1_16/602-3513816-2830240?ie=UTF8&frombrowse=1&asin=B0002EHOEE
) and the lighting situation. It's really the light, or lack of, that makes it so dark. And with off-white accessories here and there, it will contrast the red but brighten the place up. The off-white, red and black/dark brown combo would look great.