I like my SX, but it took a little work to get there. I got it as a backup and for a while all I had done with it was to swap out the stock pickups for DiMarzio J's. It sounded OK and played OK. When I started gearing up to do a proper set up on my first PitBull kit, I put a bone nut on it, dressed the frets and did a proper setup. After that it played great, but it still sounded just OK. I did a little routing and got a new pickguard to put in a P pup where the neck J pup had been, and swapped out the pickups for some EMG Geezer Butlers. Neck dive was cured with Gotoh Res-O-Lites. I think the only the bridge is stock and unmodded at this stage. I do hear you about the weight though. It's on the heavy side of the normal range for a P/J bass at about 4.5kg.
That makes sense. You'll hear yourself better in the mix when the strings are a little brighter. I think it depends a bit on your playing style as well. I like them a little dull, except for slap...which I am very bad at and don't do much ;-)