Mule neck is a bit smoother than Riff Raff - at least that seems the common opinion on these two.
Since you ruled out the Abraxas for you that would then leave you with the Emerald for the bridge spot. From what I read it does have a lot of treble.
You have probably already listened to the classic rock clips of The Mule, Riff Raff, Black Dog, Emerald and Abraxas. You may want to listen to them again.
Cheers Stephan