Be a good idea to read through the REVO section on the forum
http://www.rc-monster.com/forum/forumdisplay.php?f=24 and you will see plenty of ideas on conversions.
I good allround conversion would be the Feigao/Nemesis/Wanderer 9XL or maybe 8XL
http://www.rc-monster.com/proddetail...WAND_XL&cat=20
You don't really need to go over 5S but still me wise to get the new Castle Mamba Monster as by the time you get the Mamba Max, a fan and a BEC you nearly spent as much as a Mamba Monster which comes with all those features -
http://www.rc-monster.com/proddetail...steresc&cat=20
Read through these 2 topics and you may get some ideas
http://www.rc-monster.com/forum/showthread.php?t=11114
http://www.rc-monster.com/forum/showthread.php?t=11475