Well I don't use cad but I can give you the raw performance
Fx 540 = GeForce 6600
7450 = is a rebadged 6450
Quadro 600 = GeForce 430~
If your just looking at models the 7450 should be fine . the major difference is that firepro or quadros have optimized drivers for those types of programs . I'm guess eithers its going to be a laggy model or smooth with either card because they are both low end
Edit: if I had to choose without knowing cad( which I don't) my bets on the Quadro 600 but I couldn't tell you how much benfit it will have over a 7450. It will however crush a fx 540
Edited by hornybluecow, 29 January 2013 - 10:29 AM.
Filckr Photostream / Workstation Build Guide / How to Overclock an Intel 4770K Guide
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