Placing speakers directly in the corner will not be the best option as you more than likely will get reflections off the wall. Moving the speakers even 12 inches off the wall, however, can make a big difference in sound quality. I recommend you set it up and try out different placement scenarios. To the previous poster's point, I would HIGHLY recommend you consider a component system or start with a different HTIB.
A component system allows you to upgrade fairly easily into the future. If you go with a component system now, the upgrade options are limitless – along with the prices.
If you stay with the HTIB, I suggest something like the Yamaha YHT-390 5.1 HTIB system at about $400.00; see the link below. I suggest this due to the traditional A/V receiver you could use as you upgrade speakers in the future. The Sony you stated has a proprietary type receiver that is designed (more than likely) only for the speakers it comes with out of the box. I started this route and now have a Klipsch 5.1 reference setup with a better A/V receiver. The original A/V receiver was used for a few years with OK results.
http://www.yamaha.com/yec/products/productdetail.html?CNTID=567702&CTID=5000800
At the end of the day, it all depends on your future goals. You can buy the Sony HTIB now and then buy a great component system later. And then place the Sony HTIB in the bedroom, garage, or other room. There is always a place for something like that.
Drell