I'm still not clear on what you're looking for. A preamp to use along side the Crack, or a preamp to use in front of the Crack?
If you want an "upgrade," the Moreplay is the obvious choice, but it's not going to add any "grittiness." The Crack is probably Botllehead's "tubiest" sounding offering (in the traditional sense of sounding warm and lush at the expense of some dynamics and resolution), so if you want a tubier sounding preamp, you'll need to look elsewhere. That's not to say the Moreplay doesn't sound like a tube preamp, but it's a step up in terms of clarity and resolution.