Combo 1x12 with a G12M 8Ohm ?

[plexilove]

Hi friends,
in these days i'm thinking to keep my Ceriatone 18Watt head chassis into a 1x12 combo case!
So i'm searching for the right speaker, and could fit an old Celestion G12M-25W hms (Rola) ! But not 100% sure on this choice, because to me Marshall sound is on 16 Ohm. I'm afraid to obtain a harder tone with a 8 Ohm speaker. I'd like to check a G12H-30 16Ohm 55Hz, but it's hard to find an old one (Rola too).
Now i play my 18W head on a 1922 "Open Back Modded" 2x12 Weber Equipped (Ceramic Blue Dog 30W + Ceramic Silver Bell 30W), but i would to get an original Celestion for my 18W combo version.
What could you advice to me ? Anyone here playing 18W with a 1x12 hm speaker?
Thanks for your help

[Wayne_Alexander]

I haven't found that an 8 ohm speaker (with the amp set at 8 ohms) sounds notably different than a 16 ohm speaker (with the amp set at 16 ohms). The 16 ohm setting might be slightly dirtier/more complex but it isn't much. I have found that G12M type speakers don't sound good to me in open back cabs, they get trashy (in a bad way) at high volumes. I do like G12H and G1265 and G12 Alnico (Blue) speakers with 18 watts in 1x12s. The Blue will give you a Voxier sound, the G12H will be a bit Marshallier.

[plexilove]

Thank you very much for your reply Wayne!
I'll give 8 Ohm speaker a try