Knowndeserter is correct. Your Sony doesn't have a digital input, so you'll need to connect your DVD player via the 6 analogue inputs on the rear left of the Sony (from the viewers point of view) - see his link to the manual,
So you need to be careful about what you pick as a DVD player, as not all of them have the necessary 6 (5.1) analogue outputs.
If you got something like the
Cambridge Audio DVD99 [click] you'll be able to play DVDs, CDs, SACDs and DVD-Audio disks too (which are much higher quality than standard CDs). They're less than £100 as well, a true high quality hi-fi bargain from Richer Sounds (if there's any left, of course).
Alternatively you could buy a blu-ray player. The Sony will sound even better, and Cambridge Audio do a couple of Blu-Ray players that also cover all the high-res audio bases.