The more expensive kit of 10-15 years ago will mostly leave today's budget kit struggling behind, particularly in terms of amplification and turntables. When you think about where most of the R&D budgets have been focused since that older kit was made it is no surprise that, in terms of 2 channel musical reproduction, older kit will still outperform most of today's budget kit by a very comfortable margin. In terms of something like the Audiolab 8000A, don't forget that its latest incarnation (8000S), which is virtually the same as the original and certainly doesn't sound any better, is still far more expensive to buy new than a good example of the original would cost secondhand. I'd still say that, at £400-£500 the 8000S remains one of the nicest amplifiers at its price point.
If we look at turntables for a moment there are loads of vintage bargains to be had, many in the shape of older Rega Planar 2s and 3s which, with a modified RB250 arm (the RB250 is potentially better than the RB300 when modded) and a decent cartridge can give astounding performance. Linn LP12s can be had for around £500 on the used market and still provide the most toe-tappingly satisfying performance available for that money, although with the caveat that there are a lot of rough examples out there and that they need very careful setting up to give of their best. Around the £100-£200 market you can easily pick up decks like the Systemdeks, Revolvers, Linn Axis, Linn Basik, and Technics SL1210 which, when partnered with a good quality arm and cartridge and set up correctly will leave the current budget offerings from Pro-ject for dead. As a further example, look at Thorens. Its current budget decks are simply rebadged Dual designs (the TD170-1 is a CS-430 by another name) and for the same money you can achieve far better performance from a classic TD150MkII or TD160. Indeed, look at the current price of buying a brand new Dual CS505 (yes, they are still being made, in the same factory as Thorens and cost upwards of £400 to buy new). Because vinyl is more of a minority interest than it was in the heyday of brands like Dual and Thorens it costs so much more to get the same performance.
I'd say CD players were the main area where new is almost always better than vintage simply because of the massive improvements in digital to analogue conversion and the availability of parts. Many vintage CD players are likely to suffer from laser block or transport failure and these parts are, for many, no longer available. This is because most CD players, including the very high end ones, always purchased these parts from Sony and Philips who have stopped making some of their most widely used mechanisms. Consequently, players from budget fare such as the Marantz CD52MkII right up to some of the Naims, Arcams and Linns are now impossible to fix with new parts.
However, even with amplifiers, there is a point at which further complications have to be considered. As equipment gets older (15 years+), components start to weaken or fail and capacitors in particular can start to leak. Anyone who has re-capped an older amplifier will testify the difference it can make and so, in the terms of the present discussion, we have to consider the effects of such deterioration on performance.
There are whole swathes of audio enthusiasts who swear by vintage kit of all descriptions with very devoted followings for older, high-spec Japanese kit - amplifiers by Sansui and Pioneer in particular. This is where the need for restoration certainly becomes more of a consideration and buying becomes more of a risk although the standard of build quality on some of those amps was so superb that, with TLC, they are capable of giving years of good service.