There are more differences that it meets the eye: the 180 Bhp has stronger rods, lower CR/stronger pistons, larger nozzles and more aggressive ECU map. It's easy to get the 163Bhp to 180Bhp, the later BDG 163 Bhp engine goes to 195Bhp with a Steinbauer tuning box or a good custom remap ! The clutch is the same between the FWD and the quattro, only difference is the 180Bhp has a stronger pressure plate and a self adjusting clutch. Only issues with the FWD is their poor ability to put all that torque and power on the road without keeping the ESP on ALL the time ! Also later b6 tdi (quattro or FWD) have extra limiters built into the injector pump so they won't get over 250Bhp even with massive turbos and nozzles !
As for the pd130 engine, they are fine with a remap and some modest tuning but they tend to munch gearboxes for fun, my b6 a4 with a custom remap, bv43 and rebuilt engine stripped the syncro on 3rd in the 1st day i had the custom map for the bv43 ! My 300Bhp a6 tdi quattro is fine with 80% larger nozzles, standard clutch and custom remap + GTB2260vk hybrid turbo ! The 4 pot diesel engines are not in the same league with the v6 tdi engines !