Your "old" stock sure looks like thicker gauge metal. Don't worry about the 25 gauge in terms of the ceiling falling down. Remember that when the face is attached to drywall, the clip also becomes stiffer.
I hear you on the old construction. I'm currently doing a theater in a 100 yr + house, where knob and tube bits are everywhere. Floor joists range from 2" to 2 1/4" in width. Nails I've pulled from floor joists are square....
Rather than doing the resilient across the joists (wildly uneven) I furred them with steel studs to get to level. Presumably the metal studs perform similar to resilient channel, although in my application, who knows.
This is what I'm dealing with...the pic below was taken just after dropping an under slung fir beam, cutting 7" of floor joists away, and installing an engineered flush beam to get back some ceiling height.
Otherwise, I was facing shimming every strap, and dealing with a 1" dip over 10 ft! The steel studs were pretty straightforward once I found the low point using my laser level.
This is not my basement, but describes the method: http://www.aconcordcarpenter.com/how...a-ceiling.html