TdiBlair, I'd say if you want to go with a 35W set up, pull the trigger. It's a safe range. I've helped people install HID lights before. Some were aftermarket and some were pulled from a car that came with them. They've all been in the 30-35W range and there's never been an issue in my experience.
To be safer even, you can get a hold of or simply make a harness. This would include a relay and some fuses. This way if there's some sort of an issue, there's not going to be melted wires, but a simple blown fuse or something cheap and easy to fix.
Bi-xenon set ups are not that complicated. The simplest way to explain one is this - a single bulb is used to provide the light. When you've got your low beams on, the cut off appears as it normally would limiting some of the light output. When you switch it to high beams, a small motor/actuator moves that metal piece inside the light assembly, so that it doesnt block any of the light and you get a different light pattern. It gives out some more light, because the metal piece is no longer blocking any part of the bulb.
As far as all the "HID look" this or that claim that traditional filament bulb packages claim- it's all marketing hoo-hah. It's simply not even close. I've got a pile of boxes and some light bulbs that I've tried over the years in different cars and simply put "don't bother". They can claim whatever they want to on the package, but it's no match for actual HID lights. I'll give you a quick and dirty run down. The bulbs here are advertising that HID look, or Xenon like look and such.
You're going to notice something that stands out right away, the bulbs are blue, purple, blue-ish or have some color in them in the glass. This is the first sign of faking it. You're also going to see photos posted online that will show them pointed at things and giving off a blueish tinge or maybe purpleish. This is again, fake. They do not give off blue or blueish color. They barely show color. This is simply put- crap. Also, notice how they have a filament in the bulb itself. This tells you that it's a traditional bulb. Now, theyre going to claim that the gas inside is different or this and that. Whatever they claim is not going to match or look like actual HID lights, man. It's marketing, pretty pictures as well as a lower price all set there in order to have you buy product. They are great at selling you the sizzle and not the steak, so to speak.
Now, let's examine some HID bulbs.
This picture is massive
http://image.made-in-china.com/2f0j00iBNQfwmhELoY/HID-Xenon-D2R-D2S-D2C-Bulb.jpg
You can plainly see that the actual glass is clear. They are shaped differently, theyre more of a straw rather than a bubble. They don't have that pinched off nipple looking part of the glass at the end. They clearly have what looks like a wire or a stem on the outside of the bulb and no actual filament inside connected to two stems. You're going to see a small wire inside, going into a small bubble that has nothing inside thats visible, then another wire on the other side of the bulb. It looks like the filament is not complete. THIS is a true HID bulb filled with xenon gas. There might be some other gasses in there as well, but this is what you want. The basic principle behind standard bulbs pictured above is that they take that 12v from the car and hit that little tungsten filament that heats up in the bulb. The HID bulbs are different. The little ballast and igniter boxes(sometimes its 2, sometimes its just 1) are basically transformers. They are kind of like neon light transformers. What happens is that they take that 12v, convert it to a much different voltage thats WAY higher. I'm not going to pitch the math in this one with the ohm's law formula and such. This is needed in order to excite the gas in that little bulb in the middle. Once that current hits the gas, it glows giving off that light. The output is MUCH more lumens, the color is also going to be different.
As far as your retrofitting concerns go. Yes, it's always better to install a projector into the headlight housing if it doesn't have one. You can definitely put in a set of HID lights in your headlights as is(provided the bulb codes match) and using a 30-35W kit you would be set. You might need to adjust the headlights so you dont blind the oncoming traffic as much. It's best to use the projector, as I've stated before, because of the reflector and other reasons. I'd say, you can definitely try an HID set with OEM housings first, get a harness as well to be on the safe side as well. In some cases, the HID kits will draw less power that conventional light bulbs(yes, it can happen even though theyre so much brighter) and set off a light on your dash that indicates a bulb out. They make error code eliminators for that as well.
If youre looking at a budget of $65, just get ones from DDM(i am not affiliated with DDM in any way. I'm mentioning them as they have kits in the price range and were mentioned before in the thread), they'll run you less(most likely, unless you start getting very fancy and get every option available). Yes they advertise that theyre in the useful range of numbers in K, but it's all bunk, as I've stated before. My advice would be to snag an HID kit. It may take a little bit of fiddling with it, but its 100% worth it. Later down the road, buy projectors online, find them in a salvage yard or whatever works best for you and them adapt them to fit your headlights. There are numerous retailers online that will sell glass lens projectors for a reasonable price. Reinstall the HID kit into the projectors, align them correctly and enjoy. Don't bother with regular bulbs claiming this and that, because youre getting into the territory of those electric superchargers, magnets people put on fuel lines, fans they cram in the intake or the general areas of magical beans and snake oil.