I'll echo what Tls49 said, but do you suspect the crossover b/c you're not getting any sound output from the speaker at all? If that's the case, I'd first check to see if your speakers have any fuses (possibly a dirt simple fix)...or, if it really is the crossover then there are plenty of very reputable HiFi repair companies out there that could easily and rather cheaply do that kind of work. All you would need to be able to do is to find a way to reliably uninstall and reinstall the crossover to allow you to send it in for repair by itself (MUCH cheaper than shipping the whole speaker). But even if that was out or the speaker was otherwise effectively dead altogether, unless you're just itching to try something new, I'm supposing you could always just buy another (used) pair of the DM604's and the one you have left over now could be your center tower, if that works for you (and the center tower is not going to be too tall for your app, assuming you're not needing to go horizontal with it). Or if you have any HiFi shops within driving distance you may want to see what you might arrange to audition, or even borrow if the dealer can be worked with (just be sure not to borrow anything you can't afford ;^) But, even if all that's out, then I do believe I'd second the Monitor Audio Silvers as well.
13yr old speaker upgrade
Okay I have a pair of dm604 s3 towers. My first big boy speakers. Incredibly happy with them. But I don't know any better cause I haven't owned anything else. I have the smaller of the two center channel speakers of that B&W series. I have moved into a bigger home. And now have them in 21'x17' room that opens up into a kitchen. I have in cieling surrounds that do the job. And a JLf112 subwoofer. I'm using a onkyo 818 av reciever. Now one of my towers have failed. (Suspected crossover). I want to purchase three similar front stage speakers. Three similar towers. I kinda want to keep my budget around $3000. I am also open to maybe going cheaper on the towers and purchasing an Emotiva amplifier to really drive the speakers to pick them up in performance. Any suggestions??