Pete,
I love the Transporter as is, which has kept me from modding it. It is hard to believe much improvement can be had by modding the TP (laws of diminishing returns) but I am curious. Always looking to squeeze out that little extra.
I've also considered Modwright's tube mod, but because I use a tubed pre already, I don't think I want introduce more tube flavor.
I have heard the Benchmark in my system. It was fantastic, but to me, there was no reason to keep it as I preferred the TP DAC.
When your ready, I hope to hear your new system/room. I know you have been very busy buying new equipment and tweaking your room. If I do get out to your place, I'll bring my Transporter with me and we can compare it with your SB/DAC.
Mark