It's decent. the Cas latency has more effect on stability than bandwidth but of course this pertains to OC'ing the RAM really.
the 2nd set of 3's has more effect on bandwidth..possibly 100-200mb/sec difference if you benched it in Sandra.
As far as changing timings, that's up to your disgretion. They put it at 3 for a reason because that's it's safe settings. I have a single stick of kingston value RAM and I don't believe it liked any tighter timings, but you can try it if you want.
If you fry it, chances are you could still get it replaced by the manufacturer. I fried a stick of theirs and said "Yeah, I used a program memtest86+ to see if it was giving me errors and it gave me over 100,000" and they replaced it