Help for my E6 setting

[EdokTheTwitch]

So, I'm making a custom setting for a game with my friends, very similar to the Witcher games. Basically, I'm making a pool of level 6 characters, and at the beginning of each session, everyone rolls on a d20 and plays that specific character, in a random hunt-down-the-monster type of quest. Most of the characters are, at least in some way, melee with a dash of special powers, like spells, maneuvers and psionic powers.

So, here's what I need from the playground: I need some melee prestige classes that can be used as base classes, and roll well around the power level of initiator classes. I'll include the characters I created so far below, for some reference

Soulknife (slightly buffed), Crusader, Duskblade, Bard, Factotum, a weird Druid/Dryad/Plantshifter, Wildshape Ranger, Warlock, Psychic Warrior, Dragon Shaman (gestalt w/ Dragon Adept), Binder, Knight

The only prestige class I used so far is the Runescarred Berserker, as it does not seem too far out of order in the group, but I'm really bad at locating decent prestige classes by myself, as I usually go with E6.

Any help is appreciated :)