I have built my system up since 1999 although my current system is different from my original seperates system. Most HIFI seperates don't change electronicaly it is just the facia that does, my sister has 1970's system that still sounds good, she uses this with her computer.
My trick is to wait to the model is about to be replace you can get real bargains this way. My current system is:
Marantz PM6010OSE (was £230, I paid £150 a few months before it was discontinued)
Marantz CD6000OSE LE - A very high quality CD player, the quality of the compoents have to be seen to believed (was £330, I paid £150 2 months after discontueation)
Eltax Monitor III's - Richer Sounds staples, cost £70, not audiophile but much better than any all in one system speakers
Project Debut MKII turntable - Paid RRP of £110 3 years ago, the unit is used daily and is brilliant, the sound has to be heared to be believed, I have to replace the stylus (cost £25) yearly though.
Rotel RC 870BX preamp - Bought this second for £15, this did cost £250 in 1989. This is used for my turtable and also as a switch to select from PC and freeview box.
Sony STE 300 RDS Tuner - Paid £80 for it but hardly used now
Philips HD890 headphones, cord needs replacing due to overuse, cost me £50.
Buying HIFI seperate is probably one of the best things I have ever invested in. The shear sound quality is simply amazing. I also have a very big soft spot for Marantz products.