Yep -- check the power requirements if it's listed. Newegg.com usually lists it.
I run nVidia cards (6800 GS and 7950 GT) with 350 W power supplies in my Dell just fine. However, when I was shopping for a new card and checked the Radeon x1950 pro, it said it needed a much larger power supply, and the user comments talked about it needed something more than a skimpy power supply. I ended up picking the 7950 GT as much for that reason as performance reasons.
I've been very happy with my current nVidia 7950 GT and my previous nVidia 6800 GS. However, I have also previously been happy with Radeon's as well (had a Radeon 9600 Pro before that and several other 7xxx and 9xxx Radeons).
Basically, I go with best performance/price unless there is a mitigating factor (like power-supply requirements).
As for range of nVidia cards in the game, I'm running an nVidia card, and I seemed to see dots at the usual range, so whatever weirdness people were having, I'm not sure I'd attribute it to nVidia.
For nVidia cards, I've had very good luck with BFG and XFX brands, and bad luck with eVGA brand. For Radeon cards, I've had good luck with Sapphire and some other brands I don't remember.