more is better. more memory, more processor, more powerful graphics card... all better.

check for recommended hardware from the software company.

also, check here, http://www.cgarchitect.com/ for good info.

I just got a Dell dual 3.4, 2 gigs ram, Quadro 1400, three 250 gig drives (two running RAID 0) and a 24" LCD.
No one can beat Dell's prices and support. I looked at Boxxtech, but they are just too expensive (although I've heard great things about them).

This is how it breaks down for me:

#1 processors
#2 ram
#3 hard drives
#4 graphic card (they gave me about a grand off, so this card was pretty much free, as was the additional hard drive - they have room to bargain with).

Voodoo makes some very nice computers, pricey, but some of the best available.

ok..
rendering speed is determined by your CPU
ability to handle wireframes in your monitor is dictated by your videocard.
i have ATI fireGL, a cheaper version of a workstation grade card.. its adequate for what I do.. i can handle 500k poly model pretty well..

dell has a good deal on the 8400, $300 off anything above $900, and a free upgrade to a 19" flat panel. the ultrasharp 19" is down from $499 to $269. (all with coupons from fatwallet.com)

all together, you could expect to spend about $1200 for a pretty decent system w/ 2 19" flat panel monitors.

i just bought the same system, allowing for a few upgrades here and there, about $600 more for (2) 1gb ram, a dvd burner and a 250 gb harddrive.

good deal if you ask me for under 2 grand.

also, there are ways to overclock the consumer grade cards to the same performance as pro cards costing twice as much. try searching google for more info.

If you are using an nvidia card, make sure to install their maxtreme drivers.

The niche manufacturers, like Voodoo and Boxxtech and Falcon Northwest, probably make the fastest, best machines out there. But you pay a lot for that and if it's for business, you don't really care about the semi gloss car quality paint job (although if we could just have some kind of G4 rip off, I'd be happier).
Dell is still the best on price, at both ends of the range.

http://www.techbargains.com - keep an eye out there, the deals are really amazing at times. I am getting a laptop once that 30% comes around again. That's big savings!
Not to mention I just got my Norton Security Suite from Buy.com (ends Sat) for free! Man, I just love getting deals!

meversusyou, you have found fatwallet too, huh? Man, that site has cost me a ton of money....

alienware etc do powerful machines oriented towards games.
3d workstations have different requirements:
games dont make much use of multiple processors, but 3d modelling does. a dual processor rig will render much faster.
a video card for games is different to a video card for 3d modelling: a top-of-the-line gaming card (an nvidia 6800gt or something) may only give mediocre performance in a workstation.

if you care about performance, build your own machine. it's not that hard, just make sure you get parts that are compatible with each other.
www.arstechnica.com have recommended byo systems.

For architecture, you'd be surprised how similar the performance of, say a the Geforce 5900 (think that's what it is, I ahve it at work) and a Quadro 1300 (the other computer at work). Don't listen to the hype. If you are working with characters, that's a different story.

The only reason I got Quadro is because I made a deal and got it cheap.

Compare all the prices, but I think you'll find dell to be cheaper than building your own, if you spec part for part and consider some time for labor. Not to mention you can't hold on party reasonsible for all the parts and have to deal with each manufacturer (the "it's the graphic card" says the monitor company "nope, it's a bad monitor" says that graphic card company). Needless to say I like Dell a lot, esp. with the deal I just got and their new 24" LCD (see PC Mag for a 4.5 star review).

Sound like an add? Itry to find new companies, but nothing so far and every company I've worked at/for only have Dells.