I understand the most voicing is from the first position. In my amp the 4th position in the pre amp tube for the fx loop so i beleive this has least effect. Essentially my question is this...i switched v1 to jj's low gain pre amp 8cc...(something) and the results were outstanding over the original crappy mesa tubes. Essientlly is there MUCH more improvement to be had from replacing v2-v5 with jj's? The reason is too save cash on tubes. Im fairly certain the power amp tubes should all be replaced. Thanks.