* Spieth goes bogey-free to launch title defence * Says 'one of the best rounds I've scored' * Lee and Lowry two off the pace * McIlroy opens with a 70, Day with a 72 (Adds Day quotes, further detail) By Mark Lamport-Stokes AUGUSTA, Georgia, April 7 (Reuters) - This week's Masters always had the makings for being something extra special and it lived up to expectations on Thursday as reigning champion Jordan Spieth seized a two-shot lead after the opening round. The American's love affair with the challenging Augusta National layout continued in flawless style as he fired a six-under-par 66 to storm to the top of a high-quality leaderboard in the first of the year's four major championships. More...