I have the SX "pro" 4 string model (high mass bridge, better tuners and pickups than other SX's supposedly??) and I'm pretty happy with it. It's on par with a Squier in my novice opinion. Definitely a decent bass for the price.
I didn't do any setup other than that I raised the action a wee bit. It's 100% unshielded right now, and I'd like to shield it eventually, but it still sounds alright. Also, the pickguard cut is a little goofy around the neck, but a new pickguard is cheap.
I'd love to have a fender j some day, but till then, my SX works.
...I say go for it.