Let us know how the amp sounds with EL34's. A lot of people have posed the same question on this board, but not a lot of people have actually posted regarding how the amp actually sounds with EL34's.
I have the LSC 2x12 combo with the stock Mesa speakers. I also have a separate 2x12 Carvin Legacy speaker cabinet with Celestion Vintage 30's in it. I played my LSC through both cabinets and actually prefered the sound of the stock Mesa speakers. I found the stock Mesa speakers to be much smoother with a slightly wider frequency range. The Vintage 30's sounded good also, but much grainier on the distortion channel. On the clean channel the Mesa speakers are definately the way to go. I'm actualy considering swapping out one of the Mesa speakers with a Vintage 30 that way I get both the smoothness of the Mesa speaker and the raw grainy tone of the Vintage 30 at the same time. I have a feeling that that would be a killer combination.