There's an S520ex being sold for 200 bucks and i'm curious if its a good guitar or if i should save up for something else. im mostly into metal stuff and grunge but also like to play clean. also what would be some good pickups to replace the stocks pups in it if i do decide to get it?

The '02 S520ex was the only one made that was really worth consideration. It was MIJ, had a Superwizard neck, edge trem, and v-series pups.

Anything in the '05-'09 range was Korean or Indonesian. There have been a lot of complaints about a complete loss of sustain on these later guitars.

arent the Zr bridges good though? and what about the inf 1 & 2 pickups?

There's a LOT of debate on the ZR. I've never had one so I can't confirm either way. The complaint is that the ZR design kills the guitars sustain...... apparently by a very noticeable amount.

The INF pickups suck for anything other than starter guitars.

I have ZR equipped Ibby that sustains pretty well, sustain is one those things that can be difficult to find a single culprit, the guitar is a system, if a guitar lacks sustain it can be for a different number of reasons.

That said i have no issues with the ZR yet, but the feeling is very different from the Edge and Lo Pro Edge that i prefer.