I personally think you are making a mistake. However, its your money if you sell the M3 and get the Boxster, enjoy it in good health.
If you were talking about a 997.2S or even 991 different story, but not a Boxster.
2013 M3 Coupe-MR/BLK ZCP, ACM test pipes, BPM Stg2 dev. tune and Megan catback, more to come
Previous rides: 2011 M3 Coupe-MR/Blk
2007 Porsche 997C2S Speed Yellow/Blk sport seats
2004 BMW M3 Imola/Blk