your best bet is go to a dealer with a cd of what you listen to. put it in as many set up as they have got and listen, buy which ever sounds best to you.
ive done installs worth thousands and some that cost hundreds and unless your going flatlining in sq competions your average listener cant tell the difference, you dont have spend a fortune to have a nice system. if you like the sound of £40.00 speakers over £400.00 ones buy them. dealers will always try to make as much money as they can, its there job, just make um work for it.