it appears i was a tad mixed up on MH vs HPS... so ill go with HPS... will 100 actually work? or will i need 150 watts?

Are you referring to LPW when you say 100W? Or do you mean the bulb is a 100W bulb? If you mean the lamp is 100W, then you can grow a single pepper plant and it might do well. Maybe a bush tomato plant. Anything big will require more light. A 400W HID light will light a 4x4 area well. It needs to be approximately 12-24 inches from the canopy. Further and your light intensity is greatly diminished.

I got that info from the book I'll reference. If you are going to spend a lot of money on hydro, it stands to reason the first thing you should do is spend money on a well regarded book on the subject. It helps in determining good advice from bad advice in a forum, too. I highly recommend this book.

Van Patten, G. F. Gardening Indoors with Soil and Hydroponics. Vancouver: Van Patten, 2008. Print.

400W could do a massive tomato plant.. but im not looking for the thing to get out of control and intent to confine it to the area of a 5 gallon bucket with a cage... im actually probably going to step this up to a 150w HPS light which will give me a good chunk more lumens per square foot

but im trying to decide if i should go drip or deep water culture, and what sort of tomato variety would yield the most in a confined area

Well, if you are using a cage, you will have to keep the light a certain unreasonable distance away from the plant early on. I mean, you aren't going to wait until the plant needs the cage to put it around it, right? Aside from stronger lighting, I recommend against a cage. You could use strings hung from above so that they can be adjusted with the lighting. You want the light as close to the plants as possible. Especially with a weaker light source.

If my calculations are correct (if not please, someone, correct them): 100W Bulb = approx. 9500 lumens at 12 inches away. For a 2x2 ft area, you are talking 4 square feet. Problem is, you will need to be about 2 feet or so away for that area. That means you are down to 2375 lumens. Now, account for any growth. A 24 inch plant with leaves on the top foot only (good pruning practice) means the lower leaves are 3 feet away from the light. So, using the inverse square law you find that those leaves, not counting shading of upper leaves, are only receiving 1055 lumens per square foot. How often do you see tomato plants at only 2 feet tall? So, lets move on to 4 foot plants. You have fruit forming 18 to 24 inches up the plant on vining varieties, bush varieties may have fruit forming lower. Your lamp is at least 4 feet from the leaves where your first fruits are coming in. You are now down to 594 lumens per square foot at the 24 inch mark and 470 at the 18 inch mark. Keep using the inverse square law from there to get results for greater distance from the bulb.

Also, in case you don't already know, the best way to maximize reflected light is to use a matte white paint. Foil doesn't do it like many people (including me at one point) think. Mylar will if you have the stuff smoothed out perfectly, but it is quite pricey and its reflective surface loses efficiency shortly due to stuff getting on the surface.

A lot of hydro outlets don't even sell 100W lights due to the fact that they simply don't produce satisfactory results on the most common plants grown in hydro, which are supposedly tomatoes (and pot). The fact is that they don't make repeat business if you fail to get what you want and give up. They usually start at 250W. If you are going to stick with the 100W choice, please be sure to post your results with pictures. What I would be most interested in, of course, is the resulting taste. Unfortunately, that is a matter of individual preference unless you have a Brix meter. Tomatoes taste like crap when grown in low lighting conditions. They may look okay, but they don't contain the sugar that plants in more intense light contain. It's a matter of chemistry.

as far as the light goes, i was going to mount that on the side of the box with a reflector to cover the entire plant from top to bottom, and was already planning to line all sides of the plant except for the one id use for accessing the fruit

i might even set the plant so the only exposed side is the one facing the light, and i can just grab the box and turn it towards me to get fruit

anyone?... looking for something high yield and flavorful.. any high producing heirlooms worth growing hydroponically?