the Pro M should be. every Phanteks case so far uses majority or all screws instead of pop rivets so they tear down and rebuild eaily. can't see the Pro M being any exception. the thing is the Define S has better rad support. thanks to being slightly deeper it can barely hold a 420 in the top, but that removes the possiblity of the rear fan. it can do two 360's together in top/front and you get mounting for 3.5" and 2.5" drives behind the motherboard tray. the Pro M has more trade off with 360 rads as it can onlony hold 360/280 rads together and long rads in the front makes you losee all drive mounting except the three dedicated 2.5" drive mounts. another case that is similar is the coolermaster mastercase Pro 5. it's got less and less flexible rad support than the Pro M even though it costs alot more. it's nice looking though.