A common question that comes up by the time we want to improve our home theater system is: "Can I use my old stuffs and combine them with the new one?" Well, of course you can.
But you need some consideration if you still want to use your 'old stuff' as some parts of your new home theater.
These are some components that can give you some further consideration to decide whether you can stay with your old stuffs or go with a new one:

• Screen Display: - Considerations of TV/screen display are actually a combination of (at least) three aspects: Your screen display's size.
  Your screen display's resolution.
  Distance between you and your screen display.
  For an optimum result, you need a huge one, that is able to view high-definition image.
  Make sure your screen display is also compatible with the latest devices such as HDMI.
  Normally, for most home theaters, a bigger size is better.
  If your screen display's size is less than 27 inch, you better go for the new one.
  However, the smaller size will be more suitable if you want to locate your screen in a shorter distance, just like a few meters from you.
  
• Audio/Video Receiver: - Duplicating movie experience is the most common purpose of building your own home theater.
  So, if your old audio video receiver is not support surround sound, doesn't have built-in amplifier, or input for video devices, I strongly suggest you to go for a new one.
  
• Speakers: - Speakers get it best performance if they are used in one set.
  I mean, if you are going to buy some additional speakers and combine those new speakers with your old speakers, then you will never get a good sound.
  Unless you know how to combine your old and new speaker that come from the same brand as a complete surround sound speaker set, you better go totally with a new set of speakers.
  
• CD/DVD players: - For most case, these two devices won't need any change.
  So, you can use your old CD and DVD player as part of your new system

From 4 stuffs of your old system, normally you can only reuse your CD or DVD player.
So this just to remind you: Do some plans if you want to have a satisfying home theater system! By having such a plan, you can build your system part by part, and you can get a satisfying one for your quality digital entertainment.