I may be mistaken, but I think the MG10 has a 6.5" speaker. If I'm right, that would be your problem. It's hard to get a full tone from a 6.5" speaker. Too bad there isn't a amp out, so that you can get the Direct (DI) signal from the amp, bypassing the speaker. Then you could use IRs to hear how it really was supposed to sound.
I did something similar with a small Orange Crush that I used for my workbench amp, while testing guitars. I added an external jack, that bypasses the speaker when a plug is inserted. I played through the speaker, then inserted the speaker cable into my Mesa 4x12.
The difference is amazing, even on this little iPhone sound cliip: