I think it boils down to the amount of money put into the advertising campaign. All three that you listed above (and then throw in Voodoo, Falcon Northwest, etc) always run ads in major computer publications - but they don't wrap a lot of money into the radio/TV (or atleast I haven't seen that). Because their volume is smaller than the bigger companies you listed (my assumption), if they ran the radio/TV ads, we would probably see an increase in prices for a bit.
My first laptop was a KDS. Did not like it at all - but it was all that I could afford. I then got a Dell 8100 and absolutely loved it. When I looked to replace my Dell, I went right back to Dell and started looking at their 9100. The XPS' were not available at the time (if my memory serves me correctly). If it was, I may have stuck with Dell. That is when I found this site and started hearing about the clevo models. What turned me on was the colors. I had heard of Alienware and knew that was one of the best gaming laptops (from ads), but the price was better on the Sagers. So I spent several months here and would have ended up with a PCT 8790, but the paint options were not available at that time. If I was going to invest in a laptop, I wanted a unique one. That is when I found Hypersonic and have been with them since. My laptop history lesson is over and I hope I didn't put anyone to sleep -
If money was not an issue for me right now, I would have gone with the maxed out FX7 (the AMD powerhorse). I believe the FX7 with the FX-57 chipset and 7800 GPU is the best gaming system out there right now. This is my personal opinion as I haven't seen the user reviews stating otherwise. Sager's model is 9750. If I was to name a "best of the best," this is where I would go. But remember - this is from my gaming perspective. Everyone has their own views.
As for Hypersonic, I know you are going to get a solid performing machine. There are those who have their problems, and Hypersonic works hard at rectifying these. But this is the case with any vendor. But from my own experience, I have been completely happy with what I have owned. If I had a different opinion, I would have gone elsewhere. That said - talk with the sales people at the different places you are looking at. Look at the options available and the warranties and then review customer reviews here on NBF. I know on the Sager side, PCT has awesome customer support. The folks there always seem to be going the extra mile to work with the customer and Sager. So if you are not 100% sold on Hypersonic, then check them out as well.
Either way you go - good luck and continue to ask the questions. This forum and the members (in all the sections) are an awesome resource for answers. I owe a lot to those who helped me.