This is wonderful how you opened the stairs - you get a real sense of the architecture and it brings in more light. I applaud what you have accomplished. I'm going to assume that the wall above is patched with quickcrete and the whole thing is painted (try to get the wall beyond under the stair too). If you have / want a flat screen, you might mount a swing arm wall mount for a flat panel television on the vertical wall element remaining on the right - just about 3' - 3 1/2' (around 1 meter) above the floor so that it is eye level when you are sitting. The swing arm support will allow you to tilt the television away from the wall ever so slightly across the nearby corner. This can help to eliminate glare from the nearby window and make it possible for more people in the room to view it / expand your seating possibilities. I reference something like http://www.cdw.com/shop/products/Chief-Thinstall-TS318SU-Medium-Dual-Swing-Arm-Wall-Mount-18in-Extension/2555661.aspx?cm_mmc=ShoppingFeeds-_-GoogleBase-_-Video/Monitors/Cards/Projector-_-2555661_Chief%20Thinstall%20TS318SU%20Medium%20Dual%20Swing%20Arm%20Wall%20Mount%20-%2018%22%22%20Extension%20-%20_CIF-TS318SU You can even mount a television tlhat is wider than the wall behind as it can sit flat on the wall and extend beyond the wall to the left when at rest like another plane in your architectural composition. Since the upper stair is just behind, this should be fairly safe for the electronic. Determine precisely where the television will be at rest before you hang the mount itself. Then, look for a low height chest to sit below the television. Ideally a chest with one open shelf near the top to hold your component receivers. You may want to try to run electrical to the remaining vertical wall on the right (the support for the stair landing) to get power into the wall itself, while everything is open. Depending upon where the nearest source is, with concrete walls, you could mount the power junction box low on the wall under the stair and drill out small diameter cord passages through the wall after placement of your components. Or use the baseboard area to run needed cables and power to the area behind the chest, then conceal it with baseboard trim. The more you can hide the power and connection cords, the sleeker the look, to match your gorgeous architectural stair element. If you have a larger deeper television, put it on a sideboard chest under the upper stair where you have the depth. In the rear area, take care with putting cables together in a cord cover - ikea has a good one that is inexpensive. http://www.ikea.com/us/en/catalog/products/20097954/ so it looks "neat" from behind when you come down the stair.

The Besta from Ikea is the most easily done to fit any space this is the one mentioned above,

Sujithra, Everyone has their own costing formulas. Due to professional courtsey we wouldn't want to compare/comment on that. However, BWP ply and PVC sheets base cost is similar. Just changing carcass material the reduction in cost may not be substantial. Thanks, Nitin Cornerstone Designs Bangalore.

Just because you want to use the space below the stairs, do not just add drawers or shelfs unless you reaalllyyy need it. I would suggest go for adding something green to your house. Its healthy by adding air purifying plants. These plants are nowadays available in most of the nurseries and moreover Green patch in the house gives a beautiful look to the house and is also good for eyes ( the green color). Below are few picture to motivate you for Green patch or Indoor garden.