Most amplifiers have a few inputs you can use like "CD" "TAPE" PHONO" "AUX" etc and 99.9% of the time they will be 2xrca phono inputs, which are the standard one red one white inputs you'd find on any audio equipment.
You can buy just about any lead/cable you can think of with one end the red and white rca phono to plug into an amp and with anything you like on the other. So to connect an ipod etc you just need a lead with the red and white phonos on one end and the ipod connection on the other, which I think would be some sort of mini stereo jack plug.
I would definately recommend buying second hand. And stick to the big brand names. Sony are always a safe bet as they seem to last a lifetime. But all brands have ups and downs and buying on ebay you will generally get what you pay for. The best bit is that you can upgrade one piece at a time should you feel like you need to!
All you need really, asuming your using the old KEFs you mentioned, is a stereo amp, and a decent DVD player which will probably play any kind of disc you throw at it. All you need for the ipod and computer is the cables/leads to connect them to your amp. Oh and you'll obviously need some speaker cables!
Good Luck!!

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