Very nice. One of my favorite big-ass rock monitors, for sure. Right now, I am using a triamped set-up with the more refined 4345's and a pair of JBL SUB-1500's.
4345 more refined? I'd not be so sure about that

4350 aren't just for rock music. I'd been listening to classical music, even duets with cello and lute with a very low sound pressure and they can play quite as good as my MBL 101 D's.
I'm thinking about selling the MBL's and keeping the JBL's.
I'm waiting for a passive x-over and, in the future, when I'll have some money, I'll try an active x-over (Bryston, maybe?) and biamping.
At the moment, my two 7 B ST's are doing a great job.
With capacitor upgrades and some TLC these old large format JBL's can really perform, even when compared to the latest and greatest. 
I will not change anything in them. Their design is great and I don't think it's a good idea to change anything, neither the cables