I agree that more expensive doesn't always equal better. That being said, to me the 705 does sound better than the 602.

In my limited experience with audio equipment, I find that as the gear gets more expensive, you begin to reach a point of diminishing returns. To me, the 705's sounded better than the Studio 20's, but not "twice as better;" only slightly better. To my way of thinking, that made the Studio 20's one hell of a bargain.