So, on the off chance that someone happens to be wondering, no, it does not seem that Citadel is compatible with the PRC (it's one of the high-rated modules on the vault, is why I checked it out)...it took me some work to get it all sorted out with the outdated CEP version it uses and getting a merge together, only to log in and find "prc_hide" in my inventory.
Found out that this is because the module itself uses a custom hide for storing its own variables, and the PRC needs its custom hide for its own stuff, so...yeah.
Was going to see if Tales of a Mage works, but it uses some weird mish-mash of the CEP (when I loaded it into the toolset it demanded haks that I didn't have, that the author hadn't mentioned in the slightest, and I had no idea where to download), so gave up on that.
Personally, I'm looking for a module with a balance between combat and story (similar to the three official campaigns), that goes into the epic levels or scales like the OC modules do. (I'd like to feel like I actually -need- that 60+ dc on my spells, or that massive fort save, or 50 AC, etc, without it being a pure hack and slash)
If anyone has any insight, that would be totally great. The vault's search system is...less than stellar. >_> And sorting through various modules that use a gazillion custom haks or any version of the CEP between 1.0 and current, is kind of frustrating.