[Ryanamur]

Like Wyv said, to find Rumphy, go to the statue of Kerah. Go through the grilled hallway. At the first round room, go right. Then, in the next room, go left. Follow that til you get to the room with 3 doors on the right, 2 cubicle with levels on the left. Go towards the door on the other side of the room and pull the lever on the left. Turn around and enter the area. Go down the stair and kill Rumphy (Stones spells work great)

As far as the number of caracter in your party, that depends on your type of game play. I'm usually a solo player. However, I'll admit that past the Dragon Spire, you'll be almost unbeatable.

Keep in mind that even though you climb slower with a party of 6, that's the way the game was designed. You will be on the usual career path with that group. Consequently, with smaller group, you'll be more powerfull faster and you'll be pretty dangerous. Don't forget that there's no level cap in this game to stop your progression.