Having fallen in love with the GSD, I am working on a 3x list as well. This is my version
Gladiator II-class Star Destroyer, 95 pts Admiral Screed Assault Concussion Missiles Gladiator I-class Star Destroyer, 73 pts Demolisher Assault Concussion Missiles Gladiator I-class Star Destroyer, 66 pts Insidious Assault Concussion Missiles Soontir Fel, 18 pts 4 TIE Advanced Squadron, 48 pts Most Wanted Hyperspace Assault Dangerous Territory
I take the Insidious because, with Hyperspace Assault available, I can often get into the rear arcs very easily and the extra range helps quite a bit. There isn't much else to do with the 3 points unless I want to force initiative. Engine Techs can be nice when fighting corvette swarms but I find that the ship is maneuverable enough without them and it gives me room for the 5th fighter squadron.