Heyyo,
It depends really. Sapphire makes ati-brand vidcards, and most are great, but they do have some crappy revisions among them. Their 9600 pro and 9800 pro lineups have had some bad vidcards. The ones with the black PCB have cheap ram that tends to fail, so watch out for those. RMA them for ones with blue pcb's.
Mostly you can trust asus for mobos. They're high quality. I hear their vidcards ain't as good though.
Samsung. Put your trust in samsung. Everything they make is high quality. Their incredible monitors, their low priced ram (some are starting to come with heat spreaders with barely any price jackup! like a few bucks! it's great!), and even their dvd writer drives. Just insanely good. Crosshair and crucial ram, and kingston (though a bit pricey), and OCZ are good ram as well.
For HD's? it's hard to tell. Western Digital is the highest quality, but HD's seem to be quite prone to bad sectors out of the box. My seagate barracuda 80GB HD only has 74GB's. I should've RMA'd.. but got too lazy. Maxtor's HD's tend to be hit or miss for the smaller sized HD's (the smaller, the less reliable it seems..) so you might wanna think about getting a good HD, big and preferrably SATA.
vidcards? hmm, evga is the forum favorite, so is leadtech (a little pricey). I myself love ATI vidcards as well. They got some of the best AGP cards, but their newer lineups are overpriced I say. Pretty rediculously overpriced. It seems after the radeon 9800 pro ati kindof got too ahead of themselves and now they're bombing.. hopefully not too much, cause they're Canadian, and let's face if, if nvidia had no competition, their vidcards would be a lot more expensive than they already are...
For cpu's I like AMD's better. Always have. Ever since my AMD K6 I've loved them. Never gave me any grief. The only prob I have right now is my HSF is finished, so not the cpu's fault actually. I guess I should've left the stock HSF on cause this custom one's too beaten up, and I did get it for free so... lol.