Your Cityscape writeup seems to be missing a couple of PrCs.
Ebonmar Infiltrator: +0Reasoning based on a Rogue 5 entry (other possible entries would be anything that can manage the steep skill reqs and has two feats to burn):
Pro: Continues your role as a skillmonkey and most other roguey stuff, including Sneak Attack (+3d6 over eight levels, sadly no progression for levels 9 and 10). Provides small bonuses to focus you on your infiltrator role, including welcome bonuses to Initiative and AC. Hide in Plain Sight (Ranger variant). Blindsense (5' only, though). The real seller is that you get your own - narrowly focused but useful - spell list.
Con: Takes two very very crappy feats to qualify for, in an already (very likely) feat-strapped build. Only 6+Int skillpoints/lvl, no Use Magic Device. Assassin has a strictly better spell list, if only because it is supported in many 3.5 books. No real signature ability (you can read War&Peace in a little over an hour though
).
General note: The Ebonmar Infiltrator does what a PrC is supposed to do: sharpen (and narrow) the focus of what your character can do. Excellent design in this regard. Sadly, it's a bit lacking in giving you additional Oomph! in your chosen area of expertise.
Crimson Scourge: +1 Reasoning based on an entry combining some martial classes (Urban Ranger, Fighter, Barbarian, Hexblade...):
Pro: Full BAB, 2 good saves (Fort and Ref), 6+Int skillpoints (good list), d10 HP, easy requirements except for 8 rks in Handle Animal (wtf?!). The first few levels are nothing special otherwise: Kid Gloves (deal nonlethal damage or lethal damage without penalty), Swift Tracker (applies only to Urban Tracking), Painful Strike (highly circumstantial, unimpressive damage bonus), Immovable Heart (small bonus vs. Enchantment and Fear) - all a bit lackluster. At 5th level, you get Improved Disarm, but if you want to disarm people, you should take that feat a little earlier, I'd say. But hey, it's a free feat.
Only at 7th level (Threaten ability) does the Crimson Scourge get something really worthwhile: Not only do you get a +2 bonus on Intimidate checks to demoralize an opponent (kthx), you can also do so as a move action (yay!), and the opponent stays demoralized for 1 round per point of your Str bonus (YAY!). Now this leads to some nice and easy fear stacking, and with the right build, you can do that all by yourself. This awesome ability is worth 7 levels of a PrC with lackluster abilities, but resting on a strong chassis.
Immunity to pain and nonlethal damage (gained at 8th) and Smell of Blood (Scent ability and +3 Initiative, gained at 10th) round the PrC off nicely.
Con: The class is built on a Ranger chassis, but does not get Ranger goodies, most of all no spellcasting, but also no Fighting Style, no Favored Enemy etc. All these are replaced by merely OK abilities, of which only one really shines. Even the Threaten ability needs a certain amount of optimization to function properly. Some class abilities are so situational as not to warrant the ink they're printed with. Build might be feat strapped (lack of Bonus feats except for surprising and largely useless Improved Disarm).
General note: The Crimson Scourge is very good at what it does (bringing small-time criminals and offenders back alive). Unfortunately, this is usually not needed in an adventuring party. However, the Threaten ability is quite glorious in its own right, and works well with many many things. Do
not enter from Ranger 5, or you'll be disappointed. Optimize it, and it will become better than your fundament.