Another possibility could be to look in the other direction? I've been using Mules and Riff Raffs in various guitars for years, and I've recently acquired Stormy Mondays.
For me, it was a toss-up between trying Stormy Mondays or trying Black Dogs or Abraxas... In the end I decided to try the Stormies, knowing that if they were a bit mild for the Les Paul they were going in, then I had several other guitars that could benefit from that.
I've been stunned by the Stormies. I think they're actually "brighter" than the Mules, but I'd describe that as "clearer" - they are so very "sweet" with that brightness. Mules sound "harsh" in comparison - there's an extra rasp on top with Mules, sometimes that's what you need, but I'm wondering whether that's the "too bright" you're experiencing? I'm finding the Stormies do mellow and raunchy - and they bite plenty when I want them to... they actually turn out to be THE vintage humbucking sound I've always imagined.
I've not tried Abraxas or the others hotter than vintage, and I'm guessing they will smooth things out for you... but I thought I'd chuck my experiences with the Stormy Mondays into the pot, you never know!
