The magazines are useful for keeping up with new stuff, as long as you remember that half of it is vaporware. I usually scan John Atkinson's measurements, because they (unlike subjective reviews) are something I can't do for myself. And I subscribe to The Sensible Sound, because David Rich is now Technical Editor, and he has probably forgotten more about audio than Robert Harley will ever know.
As for pre-purchase research, it should be obvious that I don't put much stock (well, any, actually) in subjective reviews. I'll use measurements to identify worthy candidates, and then go audition for myself.