Silver solder--what wattage soldering iron?

I struggled with the same problem when I had a 40 watt Radio Shack soldering iron. A 25 watt Weller made an enormous difference. It seemed hotter despite a lower watt rating. If you plan to do more projects, get a better soldering iron. You'll save yourself a lot of time and cursing. I've heard excellent comments about this $15 station from Parts Express:

Stahl Tools Variable Temperature Soldering Station

is it possible to have *too much* solder on a cartridge clip? I've since remounted the arm on the table and everything sounds as it should, so apparently my solder joints are competent, but still I wonder if the amount of solder has any effect on the sound

Will, as long as the joints are good, a little extra solder won't harm the sound. For what it's worth, the Incognito requires soldering the cartridge clips.