Can't speak to the MCARBO stuff, but I installed a YODAVE trigger spring in my Tikka T3X TAC A1 and couldn't be happier. Massive change for minimal investment.
I've used all of these Eley, Mcarbo, Yodave, Mountain Tactical and couldn't tell the difference between any of them.
Just pick your poison and get the one with the least expensive shipping.....