I have also seen along the years that most Linux supported hardware has more quality than hardware not supported by Linux because most Linux users choose wisely what is the best hardware to buy and they only develop drivers for them.
Always take a look at the level of support of any hardware prior buying it:
- Image scanner: SANE: Supported Devices
- Printer: OpenPrinting database - Printer Listings
- Sound card: ALSA SoundCard Matrix. Most cheap sound chips are supported in Linux. You will not need anything else unless you are a musician.
- Video Display: X.Org Video Drivers. I do not recommend any make other than Intel GMA. Intel also has very good Linux support having various engineers working full time resolving issues to make their hardware more Linux compatible. Intel Centrino hardware is always a good bet as all their components are supported by Linux. Nvidia has very bad support for Linux (they only provide closed source drivers and of much less quality than MSWindows ones). If you are a gamer you have to stick with MSWindows and pay for it or just buy a recent video game console and just be safe.
- Wi-Fi: Linux wireless LAN support. If you stick with Intel Centrino you should not have any problems.