Richard - you'll get lots of opinions. :) It depends on what you need - what do you do with your computer? Is it primarily for just web surfing, Email, writing Word documents, some spreadsheets? Or do you do digital video editing, heavy photo editing, heavy graphic games? Do you want a desktop or a laptop? The sweet spot is somewhere around $900-1000 these days - it strikes a good balance between price/performance for most people on desktops - slightly higher than that for laptops.
Masaki