Hello all! My first post here!

I own this little amp, Marshall Valvestate VS15 for over 10 yrs now, and there's need for speaker upgrade.
Primarily this amp serves as my monitor (I connect my Rocktron Utopia directly into PA) and it's 8" speaker doesn't
do my ears well 
So I wanted to upgrade to 10" speaker and was told by some not to do that, and by some - go ahead!

I decided to go ahead - but then I thought that maybe it would be possible to upgrade some components
also and make that - say -25-30 W amp?

If there's someone familiar with this circuitry (it's not an MG series) and possibilities of that kind of upgrade -
I'd like you to comment on that.

Thanks in advance!
Klemen