Well, first off, there aren't any off name brands per say.
Nvidia and AMD/ATI makes the actual GPU chip and then license other third-party companies to make the PCB (printed circuit board) and they stick those GPU chips on them, along with any modifications of their own (ie. extra ram, clock settings, etc).
XFX, MSI, Gigabyte, Asus, HIS, Visiontek, eVGA, and so on are these third-party companies that make the boards using the chips they get from Nvidia and AMD/ATI. Certain companies make them only for Nvidia and certain other companies only for AMD/ATI. For the most part, they are all fairly good but some companies are more reputable than others. In my opinion, on the Nvidia side, you can't go wrong with XFX or eVGA. And on the AMD/ATI side, Visiontek and Sapphire are two of the more well know board makers...but as I said...most of them are usually pretty good, it really comes down to personal experience/preference on who you go with...keeping in mind that some companies either overclock their vid cards, or add ridiculous amounts of RAM, or specialized coolers, and so on. So not all of them are going to be exactly the same. A company might release a version of the 8800GT with the standard cooler, and then release the same card but with a different cooler on it. Or they might release a card running at 600MHz core speed and another one at 660MHz. Or the RAM might be different. This is really where you get tons and tons of different vid cards, because each company usually releases at least 2 different versions of the same card.
If anything might be considered an off name brand it's only because they aren't as well known for their vid cards as XFX or Visiontek for example. A company named Galaxy made a version of the 8800GT, but I would venture to say that most people have never heard of Galaxy as a video card maker before and might avoid them because it isn't such a recognizable brand, but that's really the closest thing to an off name brand regarding video cards, just name recognition. Doesn't necessarily mean there's something wrong with the card.
In the 8800 series, it is usually broken down like this.
GT < GTS < GTX < Ultra.
Now there are some exceptions to this, especially recently with Nvidia's new 8800GT (G92 Chip), which is better than the older GTS (G80 Chip) cards. But there are also newer GTS cards using the G92 Chip as well, so these are still better than the GT. In the GTS line, you can tell the difference between a G80 and a G92 chip depending on the RAM. If it has 320 or 640 MB it's the older G80 chip. A 512MB GTS will be of the newer G92 design.
I know I know, confusing as hell. Not sure if I explained it clearly, but hopefully that will help you start to figure things out.
If you are looking to buy a new vid card, and you don't have all the money in the world to spend, the 8800 GT is considered by many to hit the price/performance ratio "sweet spot." They can run around $250 but they are starting to come down in price. I would recommend the 512MB version because 256MB of RAM on any card just doesn't cut it anymore in the newest games.
On the AMD/ATI side, the 3850 and the 3870 are also amazing cards and they are fantastic performers for the price. The 8800 GT will usually beat them in most games, but quite often only by a small margin, and even the 3850 has had some better performance in a couple of games, mainly games using Valve's Source game engine (HalfLife2/Team Fortress2). The 3850 can be as low as $150 now and also comes in 256 and 512MB versions. The RAM difference doesn't seem to affect the 3850 as much as other cards would, but it's probably still a better idea to go with a 512MB version of the 3850 anyway. If you are gaming using Vista and DirectX 10, get the 8800GT for now. The 3850/3870 take a bit of a hit in performance using DX10, but that should be fixed with newer drivers, just need a little patience.
Personally, I have a 3850 512MB OC card made by Visiontek right now, and I love it. I bought it at $180 when the 8800 GT's were still around $250-260 for the cheapest ones, so that extra ~$70-80 didn't seem worthwhile for the handful of extra frames per second. Crysis runs great at all High settings so I'm happy with it. But like I said, the 8800GT is coming down in price now so it's definitely more appealing than ever.