Long XLR interconnect for Pre/Amp?

I need 7m cables between my ARC LS15 (NOS tubes) and Manley Designer Ref 250 mono amps (10 EL34 tubes per chassis). While in transition I've been using Tara Reference RCA's; however, I've AGAIN discovered how much better my system sounds with decent XLR interconnects. I'm leaning toward Transparent Ultra or Reference (a little salty) or the newer MIT Shotgun. Both don't gouge you (as much) for the additional length. Recommendations?? Rest of system: MSB LinkDac III (transition piece), Avalon Eclipse Speakers, 5' Synergistic Sig #2/#3 Shotgun speaker cables, Transparent Super RCA's between DAC and Pre, Synergistic Master AC Couplers on DAC and Pre.
The whole point of balanced XLR's is long runs, a standard used in the pro audio biz. Whatever you choose should be fine.
Anyone have any recommendations? New MIT Shotgun? Transparent Ultra? Synergistic (?)?