Thanks guys, I appreciate all the help.

The filter is a bandpass filter (the IF is 45MHz), though, so don't I really
need a triplexor if I really want to wideband terminate the mixer "nicely?"
(Low-, band-, and high-pass outputs.) Although my understanding is that
"triplexor" in this context can consist of a single inductor for the low-pass
port and a single capacitor for the high-pass port, which certainly is quite
doable.

---Joel