I'm surprised the "boys" here haven't stopped by to comment, and while I am no authority on neither the Lyra Titan i, or Manley Steelhead, I might be able to help, and fill in, while the fellas are absent?
If Neil (nsgarch) were to stop in, he probably suggest the 25X rule, using this number as a multiplier times the internal inpedance of the Cartridge (In Ohms)
So, with that being said, and if the internal impedance was 4 Ohms, that would mean an optimum load setting of 100 Ohms.
In regards to this, I understand there is of course leeway with a Cartridge such as virtually all of the Lyras, as well as other brands, and you'd probably find that many users do indeed load these Cartridges to 47K Ohms, just like a MM Cartridge, and are perfectly happy with the sound.
Mr. J. Carr of Lyra does stop in here from time to time, and since he designed these Cartridges, he's no doubt "The Man with the Plan", and can certainly make better recommendations than I can.
I'd probably be correct in saying at this point, with the Cartridge not having many hours on it, you'll probably notice little difference, no matter what load settings you try. This Cartridge is no doubt far from exhibiting its best sound, and J Carr, and others can give you a more exact figure when this Cartridge should essentially be fully broken in. (The Archives might help you in this department, just search Lyra under the Analog Section)
Then after break-in will be the time, to try different settings, and to note how the sound is, and the best advice I can give, is to load it to the best sound that you like, there's really no wrong one can do to a Cartridge with different loading settings. Sometimes 47K might sound a little bit too loose, and lacking control.
As for your Manley's Gain, if the Titan i has the gain that I think it does, which I've seen listed in two publications as being .5mv, then 65db Gain might be a tad too high-hot?
Don't use the volume level comparison of your CD Player to judge what will work best. If the Titan is indeed .5mv, I would think a setting closer to 58db-60db max might be a better choice. With gain set too high, things might get raw sounding, akin to like your overdiving a guitar amplifier. Listen for cleanliness of sound, best combination of quiet background from the Manley, yet with enough gain to not make the Cartridge sound anemic, and that you have to crank that Mac Pre-Amp to 79 to get loud sound.
I think good advice would be to rely a bit more on the MAc's Gain Control, rather than having it too much at the Manley, that perhaps an incorrect setting would be when the Mac's readout is at 12, you're blowing yourself out of the house!
Definitely read the archives, there's mucho info on all the Lyras. Mark