[quotemsg=6760539,2,117361]Manufacturer does not matter. They all use the same reference board when they build their video cards. They just add their own style of cooling or overclock the board.[/quotemsg]
Manufacture does matter. Better brands usually use better components making the same cards others make but last a bit longer as well as customer service and better warranty is offered by better companies. Evga for instance both my gtx260 have life time warranty. If your on a cheap budget go with any card but if you are a heavy gamer and overclock i suggest you go with a good brand in case something happens. I have seen many people repurchase cards since there warranty did not cover them.
They all use the same chipset, which 90% of the home market comprises either ATI/AMD or nVidia. There is a basic reference design that the manufacture's must follow closely in accordance with ATI and nVidias license/specifications to manufacture. But some parts as mentioned above, like cooling, BIOS tweaks, memory, etc set brands apart from each other in some way. In time, people have made decisions based on the experience of others or their own personal experiences. Some people form valid points that can be applied directly, "the fan on that Duramax GTX 295 is really loud" or "the card would not work when I bought it, and it took me 3 weeks to get someone to answer the phone at customer service" Warranties and customer service are important to some people, to others (like me) we could care less.
For every person who has good things to say about a certain manufacturer, there is going to be someone who has had an equally bad experience with them. I buy from retail stores. It is a little more expensive, but I find that if there is a problem, it is going to be right out of the box. And if it don't work, I go straight back to the store and get one that does. I don't argue, haggle and wait for a week, or two, or three, 5 phone calls and 15 emails. I have better things to do with my time than deal with nonsense and returns via UPS, Fedex, or snail mail.
I also would never buy anything made by EVGA.
[quotemsg=6760498,1,284569]Well I heard people saying geforce 8400, 8600, nvidia etc... how do I know which is best and what company like asus, intel, etc made of the graphics card they are talking about.[/quotemsg]
Welcome to the forums!
See This Chart for a quick overview of how the GPUs you are hearing about will perform relative to each other.
The preceding article will also give you a good run down of the best cards for the cash.
There are really only two GPU companies that you need to worry about, ATI and nVidia.
They make the chips and design the reference boards and cooling.
Everyone selling their cards (with the exception of some custom designed boards or those with custom cooling and factory overclocks) are selling you the exact same thing, normally only differentiated by the warranty.
As for the rest, break your namesake and do some Googling of your own