Murillo...I don't think your observation that Wilson only showcases the Maxx's with SS (Krell or others) is accurate. Here are blog entries from a few audio shows showing the Maxx 3s being driven by tubes:
CES 2010: http://blog.stereophile.com/ces2010/super_priced_lamm_system/
SSI 2009: http://blog.stereophile.com/ssi2009/wilsons_to_the_maxx/
CES 2010: http://blog.stereophile.com/ces2010/super_priced_lamm_system/
SSI 2009: http://blog.stereophile.com/ssi2009/wilsons_to_the_maxx/