Is the 55 W how much energy each bulb uses, or is it the light output equivalent of incandescents? Are they pin-type or screw-ins? Judging by your plants, you will need relatively high light. Some require less light (selaginella and F. pumila), but you can always place them accordingly (further from the lights), and they will also adapt to higher light levels just fine. If your bulbs are pin-types, you could probably get away with two bulbs. If the screw-ins, you'll likely need 3 or 4 in order to have good light distribution, and avoid the 'spotlight' effect. Post pics when it's all set up!

55 is the amount of energy used. They are square pin type compact flourescents. I wanted to go with 4, I'm just worried about it being too much for some of the plants. If not, then I'm pretty much set. Pics won't be for a while, the tank has a very long way to go...but I will try to get pics of my other two terrariums sometime soon.

4 55W is a lot of light! I would initially raise the whole light fixture off of the tank about a foot. Lower it gradually, so that you don't burn any of the plants. Any plant that has been sitting in lower light for only a week would burn from that much sudden illumination. Is your tank a 75 gal. tall, or just a normal one? If it's a tall, you might be able to get away with that much light right away, depending on how tall. What are the dimentions?

It is a standard 75 gallon aquarium. 48 x 18 x 18 I THINK. I'd go with a 2x 55W compact, but I was afraid that the plants in the back on the top of the background would not get any light with the fixture in the middle or front of the terrarium. Should I maybe put a 48" standard flourescent to help illuminate the back instead? Or do the compacts actually spread out the light rather well?

How well the light is spread over your tank depends entirely on your reflector. For this reason, I have a reflector that covers almost the entire top of my tank. I didn't have this good reflector at first though, and I did put a 48" strip light across the back, and it did help, so yes, that's a good idea. My tank is an 85, almost the same as yours. Mine is 23" high though.

yea...I don't have one of those :-P where did you get yours? I have no problem though with putting a single or double tube 48" strip in the back though, if you think that will be sufficient. I'll probably just get 1 2x 55W strip and see how it works, and work it out from there though.

I have a tank with the same dimensions (75 gal). I use 3 lightstrips, 2 double and 1 single bulb. That's 5 x 40W (48") using 2 Chroma 75, 2 Vita-lite (daylights) and 1 Gro-lux. I started with a single bulb, then 3 and was still not happy. So I added the second double strip. It's still not overkill but gets a nice even illumination. Plus I connected all 3 strips to separate timers to create a "sunrise"/"sunset" scenario in the morning and at night by turning the strips on or off sequentially in a 30 min interval. Of course that's just a little gimmick, but it's kinda neat to see it getting darker in there at night with the Gro-lux being turned off last cloaking everything in a reddish color for the final minutes. Anyway, in your case I'd go with 2 double strips (4 bulbs). It really makes a differences, especially for the nepenthes (although your other plants will enjoy the extra light too). You also have to consider that your plants will grow and some will eventually start blocking too much light from getting to the plants located closer to the surface unless you have more than 1 strip to get different angles to cover the whole area.

I did find that just one normal fluo was enough to light the back where my first reflector didn't reach. It wasn't even a VHO or anything. But if you want to go with all four bulbs, like Hoschi says, go for it! A normal fluo would be enough, but your plants would really love more light, as long as they don't get burned by it. Try to acclimatize them gradually.

Would 2 triple tube fluorescents do the same job? it comes out to 10 watts more than the four compact fluorescents, but does the light output change? The triple tubes would be cheaper, and though I'm trying not to let price effect quality too much, I can't push it :-P haha

Yes, I can almost guarantee that the light output would change. What you really need to look at are the lumens. That is the light output. Watts are just the amount of energy used to run the lights. They are only a general guidline to the light output. The package should say how many lumens each puts out, and then you can figure out which is better. My bet goes with the compacts. =)