for the Netherlands, check out tweakers.net[1] for your computer parts (they have an extensive price guide that will show you which webshop has the best prices and delivery speed). If you need them in a pinch, MediaMarkt/Saturn usually has what you need at a premium.
for living room furniture... Most of it is from IKEA
for living room furniture... Most of it is from IKEA
[1]: https://tweakers.net/pricewatch/#highlightCat:14