Back to the original question, if the edwardian needs extra warmth,
another good bet would be a 25 or 40 watt incandescent. I suggest this
because using halide or fluorescent ballasts to warm the enclosure will
only be effective when the lights are on. The biggest concern for lower
temps is likely to be late at night or very early - say 3-5AM. Your
house will usually be coolist at this time, as are outdoor temps.
An incandescent is actually a lousy light source, except for maybe us
humans, but a good heat source. Even during the short winter light
cycle you can leave the incandscent on without providing any real light
to your Nepenthes, while still providing viewing and warmth.
I would guess that two 25 watt bulbs for heat would be more than enough for a
dislay case even as large as described.
Tom
Massey@hal.fmhi.usf.edu