You seem to be quite sure. Could you elaborate.DTH TV (which cable/Sat is based on) will be 720P/1080I for the next 10 years. Blu Ray won't be capable of it. Internet speeds capable of providing it will need to be 10 times faster than they are now.
you said you will watch TV and listen to music. Neither of these are Dolby surround sound encoded - meaning the audio is going to be 2 channel not 5 or 7 channel.
Many others far wiser have said this and I will say it as well - please consider a good strong stereo integrated amp with a pair of bookshelves and an active sub.
Very wise advise. Unless you watch movies from Bluray or may be even ripped blurays from hard disks / pen drives, it doesn't make sense to invest in a 5.1 system. At a given price point, a 2 channel amplifier will have far superior sound quality that a 5 channel receiver. Also, investing a certain amount of money in a pair of speakers would be wiser than in 5.1 set.
Hope this makes sense to you.