An ext. cab will help take the load off. That cured the mud on my LSC with C-90's. I put some webers in an ext. cab. If your thinking new speakers for the combo, I don't think anything will do it. Those v-30's are pretty efficent. If there is a speaker that will, it will cost $200-300 ie: EV Black label etc. Also try a different speaker jack. Like the 4 ohm jack. And lastly you could consider a retube and or experiment with the tube rectifier option switch in 50w tube rectifer. I even had some improvement with a BBE stomp. I did all of the above, but the most significant change was the ext. cab. I can certainly say that I don't regret any of these upgrades even though it cost me hundreds, Cause my sound is much better. I also tried those webers in my combo and they didn't sound as good as the C-90's did, and I fried one of C-90's apparently during the unsoldering process. That cost me $100 bucks to replace. Fortunately they have em in stock in hollywood. Moral to the story...Mesa probably put in the right speaker in for that amp.