Well, I started this brouhaha so I guess I should offer a final comment, and a bit explanation for the basis of the OP. I have found the responses to be very informative, and the bottom line, unfortunately is "it all depends".
WARNING- This is going to ramble on a bit but bear with me.
I am a one-man local remodeling contractor who occasionally gets a chance to design and build custom cabinetry and furniture. A few years ago I stumbled across eCabinets and tried it out, but never used it much until recently. I am also an ex-IT/Telecom guy (20+ yrs) who was there to evaluate the original IBM PC 64K (yes 64K) dual-floppy (NO hard drives yet) machine for corporate use. I'm also an inveterate d-i-yer and a techie at heart, so I play around with and on the PC more than I should.
I am currently running on a 5+ yr old Dell4600, P4/2,4MHz, 1G RAM (mixed speeds - not optimal), 55G hard drive w/17G free, ATI Radeon 9000 AIO video card 64Mb(w/TV). The system is still serviceable, and runs most of the stuff I do pretty well, but it is getting tired and cluttered and newer apps take longer than I like to wait sometimes, so I decided to look at a new system (BTW This is from the perspective of someone who ran TELETYPE networks in the air transport industry, operating at a blazing 15 bps).
New system because I don't dare try to dismantle this one and upgrade it - 20 years worth of business and personal records; backed-up, yes but

fear of re-installing.
I have a very reliable 'in-house' tech support helper - my son is an RPI M.E. with computer savvy far beyond mine, who is also something of a CAD/CAM expert, and who is a Software QA manager for Parametric Technology and knows Pro-Engineer inside-out (folks like Boeing use it to design stuff like 777 airliners).
He and I have built more than a few PC's over the years, and he's still in the thick of it every day, and every bit the d-i-yer himself. (I'm flattered that he still asks me for advice occasionally).
The specs I posted were for a system that could be put together for around $600 or less, provide lots more capability and capacity than I have now, and be incrementally upgradeable with open-market parts for several more years.
He has the ATI 4670/512MB video card running on one of his PCs and it will run Pro-E renderings with little effort. It does have OpenGL support. And it can be had in the range of $50. T paraphrase Glenn Warner, if I should be fortunate enough to get a job requiring the extended rendering capability of the Nvidia Quadro, I'll buy one and sell this one.
Thank you all again for the commentary, and I'll report the results of the new system after I get it up and running alongside this one (PS I haven't tried opening Kerry's Stage file yet but I doubt it will run on this system)
I'm also going to copy-post this in Dan's new thread on graphics cards and finish up there.