Still great after all these years-Dunlavy SC IVs

Driven by a Marsh Sound Design A400(200/per)and a C-J CT 5 pre amp. Every time I think I want something "better" and listen to several, I learn how much I would have to spend to get somewhat better sound. Talk about diminishing returns!
If it works for you why change?
I still believe dunlavy can give any speaker today a run for their money;I agree with Johnk as well.
Jdurrett, I'll bet your system sounds great. Hold on to those SC 4's. I have had a pair of SC 3's for 12 years. And although my amps, pre-amps, turntable and digital have all been upgraded since then, I'd never get rid of the Dunlavys. I can imagine the 4's in my rig would sound awesome as well. Good luck.
Ditto, ditto, ditto.
I have friends with Duntech Sovereigns. Keep your speakers, but you can probably greatly improve the crossover and soon you may need to replace the surrounds on the drivers.
You may try better IC or SCs, the bass repsonse of my SC-IV improved version has gone up a few notches after the cable upgrade.

Tbg: can you please elaborate on the improvement of the xo? Change the design of simply replace the caps?
Good design does not deteriorate. Foam surrounds and electrolytic caps may need replacement in time but quality design and construction will hold up.

I owned Duntech Princesses, the older sibling to the DAL SC-IV, for 19 years. My reason for selling them was to downsize to something physically smaller. I miss them.
I've said this several times before, having owned both, the IVAs are much better than the IVs in terms of driver integration.

Downsides: They are huge and heavy (and not particularly attractive)!