I installed the Ruby 6L6's last week and have gigged on them twice. There is an improvement in the tone. Not a big difference, but a more alive sound with some harmonic feedback appearing sooner and more often. The cleans are more articulate, the gritty tones don't get flubby at soft or loud volumes. The stock Mesa 430's my amp came with were fine in my opinion. Put this tube swap approached a GAS attack. The Ruby's are the new stock 440's Mesa is using.
I'm glad I did this swap just to get the experience. The improved tone is gravy even though it is slight. The guys I sat in with at a BBQ Saturday, said the LSC and Anderson Strat were sweet sounding.