I got the TAD 6L6GCSTR's in and have had some time to play with them. Whoa! These are good! I'm not knocking the Ruby's, but these have a very distinct character that took a step in the direction I was looking to go.
On channel 3 and 4, the TADs are chunkier than the Ruby's, especially in the high end. If you play a heavy low-end power chord riff, you can hear the pick releases really well. There's a lot of definition. It could almost be described as compression on the transients, if that makes any sense.
The low-end of the TADs is nice too. It's more of a grinding type of tone, a slight departure from the smoothness of other 6L6s I've tried. I can see why TAD mentioned nu-metal in their blurb on these. You could get there if you wanted to dial that tone in.
Channel 4 in particular turns into something beastly heavy. I'm not really sure how to describe it other than that, but I like it.
Channel 2 might have suffered slightly with these tubes. I'd say channel 2 likes something a bit more smooth. I have to keep the gain down just a bit lower now.
Channel 1 sounds beautiful. It's clear, airy, defined, very BIG, but without being boomy. There's a lot of high-end shimmer as well, but without being harsh.
I've been running Shuguang 12AX7s. I tried a "Mullard Reissue" which was just released in V1. Too smooth for me. I went back to Shuguangs for all preamp spots. The combination of those and the TAD 6L6s is really nice. Especially for channel 3 and 4, it results in some really great responses on pick attack/release.
Bottom line, I'd highly recommend these. I'll probably try a set of Ruby's again in the future. But the TADs are worth a shot for your next set if you're looking to experiment. These have made my VH4 sound the most unique out of all the tubes I have tried.