I think getting a sports cat is the best compromise.
I have installed a Sports cat and a Supersprint S/S from Cat-back, Supersprint Backbox with OO outlets.
I would say very minimal loss of torque at low revs.
I noticed a shift of torque up the rev range with a more rapid and keener pull at 5+ -. the redline . . . which i love as i think my exhaust comes alive after 3 anyway.
On top of that i noticed a much snappier throttle response,
a more tingy raspy note which i also love.
( but i did change all components together so i am commenting collectively)
Noise i would say depends on how you drive it.
For example in 5th @ 100kph it is really not noticable, but drop it down 4 - 3 shift with a blip in between, drop your foot and the whole bottom of the car seems to come alive with noise! so so sweet.
But i know what you mean about the 2k drone factor on a straight pipe instead of a cat.. exactly why i chose a sports cat, i get minimal droning and only for a few hundred certain revs.
The worst thing is when you have an exhaust that doesn't change it's note... no character.
I took this clip about 3 weeks ago to show the exhaust note from standing start accelerating under load... maybe it gives you some idea.
YouTube - Alfa Romeo 156 Twinspark Supersprint Exhaust