Just as Mario said, if you want a bigger sound you'll need more speakers.
Speaker swap is good for a different sound but the MC90 you have gives a sound as big as you can get with a 1x12.
I've got a Nomad 45 too and I bought a Carvin Legacy 2x12 cab with V30s. Big improvement, my amp seemed to breath better with a more relaxed tone.
Then I decided the V30 seemed smoother than the MC90 especially for lead tones so I bought an extra V30 for the combo. But then 3 V30s were a bit overdone to my ear so I bought a G12H30 16Ohm to put in the Carvin cab and I can confirm waht many people say: a V30/G12H30 combination in a 2x12 sounds really great.
So now I stopped using the Nomad speaker and use only the modified Carvin cab. Even think about building a head enclosure for the Nomad, less to haul around!
Well in short I'd say that for me 2x12 is much better than 1x12 and still better than 3x12.
So you might want to go for an extra 1x12 cab with a V30, works well with the MC90. You could also try a G12H30/MC90 combi, it might work well too.
It's an investment but those Celestion (the classis serie not the Heritage) cost no more than a Boss pedal and resell quite easily. Worth the experiment in my opinion
Fabien
