The thing to bear in mind with light, is that the amount of light you use doesn´t matter persay once you get past the base intensity needed for the correct exposure. This is to say that the exposure isn´t determined by whether or not you have a 10k light pointed at an actor or a 20k. The brightness of the actor will be determined not by the light source in this case, but by the exposure you choose to work with (i.e. f stop). Getting to your question, every scene almost needs a certain base exposure to help things along a bit, since most practical light sources don´t provide enough intensity to adequately light a scene. Especially with the kind of lenses you´re probably using.
To amplify the light in a scene, you can take a number of routes. And mind you I´m assuming this is zero budget, no money kind of filmmaking we´re talking here.
1. Bounce light off a ceiling or a white card, or through a transparent fabric. This will give an overall soft ambient light that can be controled either through dimmers if you can afford them, or through the thickness of whatever fabric you can find. Additionally, if you can use really cheap gels and diffusers that you can buy off the internet to control intensity and color. This method will get you the base exposure you need in order to give whatever other lights you have going on (i.e. flashing christmas lights or a lamp) definition.
A brief note: Lighting is all about contrast. Just because you light the room to an f5.6 with just ambient light using the above method doesn´t mean you end up with a flat scene. It means that if you want more contrast, you key your actor to an f8 or f11 (i.e. using a brighter, more directional source). Mixing hard and soft sources is a great way to make certain parts of a scene pop, especially your actors. Soft light is great for set/tone lights because it doesn´t call a lot of attention to itself in these instances because it doesn´t cause abtrusive shadows in most cases (of course this depends on the style of the movie). Hard light sources are much more dangerous, because you must always be able to justify whatever shadows occur as a result of you pointing hte light at someone or something. It is for this reason that most light is in some way or another softened, especially for actors and actresses (not to mention the beautifying qualities that accompany softer lighting).
2. The second way to make whatever lighting effect you want to be more prominant (and this would apply to the candle situation you described), is to use more directional lighting that is focused on a particular part of the scene as a means of amplifying whatever effect you are going for. For example, you have a candle in a table. Ideally, to amplify it, I would put a light directly above the candle, attach a snoot, and maybe diffuse it a bit around the edges by either unfocusing the light, or adding diffusion. Boom. Suddenly much more intensity from the candle, and it makes sense, because the light above is emitting the same quality of light as the candle. The trick in accentuating sources is to imitate the quality and direction of whatever practical you have. If you have a practical lamp that isn´t giving off enough light for you, and you can´t replace the bulb, then you need to acentuate it by bringing in a light that you can manipulate to imitate the purpose of that lamp. The problem that arises in doing this, is that it gives you the exposure you need from the lamp, but it creates an imbalance in relation to the other light sources in the scene. Sometimes this is desireable. Most often it isn´t. You then have to use other light sources to balance the adjustments you make to one. Everything has to work together.
3. Replace the lamps with higher power bulbs. This is the most expensive, and most practical way to get more intensity in a scene. I have seldom used it, rarely having a budget that would allow for such extravagances. Even though its the equivelant of paperclips on a professional movie set with a budget.
Hope this is helpful.
