Advice on hardware upgrade for Linux workstation

Hello, everybody,

I'm thinking to upgrade my personal machine to start doing more serious jobs now that my experience with Linux and CAE is grown (in big part thanks to CAELinux ). So I would like you to advise me on the purchase for a new graphics card, because despite this is an already burned up topic in many palces, most of the information is based on the formula "Windows + harcore gamer".
So, my present machine has the following:

- Processor: AMD Athlon II X4 960T (3GHz)
- RAM: Kingston 8GB
- Motherboard: M5A78L-M LX
- Graphics card: only the onboard one, Radeon HD3000/RS780L
- Hard Drive: SATA II Western Digital WD5000AAKX-0 (500GB)
- Power supply: a lemon with a copper and a coal piece

And for the budget I'm willing to sacrifice the graphic card options are the following:

- NVidia Quadro 600
- NVidia Quadro K600
- NVidia Geforce GTX 650
- NVidia Geforce GTX 650Ti
- NVidia Geforce GTX 560

The reason I list only NVidia is because many users have told me AMD drivers are behind NVidia's under Linux (we are always talking about propietary drivers). If this not the case, feel free to suggest AMD in the price range above.
What will I do with the upgraded machine? Mainly CAD and CFD. I use DrafSight and FreeCAD, and I may start using Blender. I'm also considering buying a license for Siemens NX as it has a Linux native version, but this only a plan so far (anyway, they'll be litle assemblies). For CFD I use Gmsh, Salome, Code_Saturne and Paraview. I will do simulations with up to 5e6 elements, and perhaps up to 1e7 elements on occation. For the moment I have no intentions of using CUDA. Oh, very important, I'll also use two full-HD monitors.
Well, I'm looking forward to hearing from you, people
Best regards,


César

Here is a review published in April 2013 that might help:
15-Way Open vs. Closed Source NVIDIA/AMD Linux GPU Comparison
www.phoronix.com/scan.php?page=article&i...d_nvidia_15way&num=1

Edit:
CAElinux 2011 loads on the following with no errors and the graphics is very fast.
AMD Phenom II 980 with tower style heatsink added to eliminate throttling when using stock heatsink
Gigabyte GA-MA785GM-US2H 8Gb ddr2 800 memory
Radeon 4870 512Mb attached to 2x(1980x1200) monitors

possibly try using a 4000 series card for no hassle cheap video? my 4870 cost $54 but that was a lucky sale on newegg

2nd Edit:
An article discussing the state of drivers for the AMD HD 4XXX series drivers posted 17May2013
www.phoronix.com/scan.php?page=article&i...mesa_92_hd4870&num=4

I've been running various quadro (1000, 1500, 4600) and geforce (from 2 to 6150go) cards over the last years, mainly using VariCAD. I don't think I can feel a difference between geforce and quadro running OpenGL-based CAE-Software on Linux, so a cheaper geforce card would be ok. Of course the binary nvidia-driver is necessary, no chance with nouveau yet.
I also use a notebook with an Intel HD4000 which performs really bad under VariCAD.
The reason for me to run quadro cards is I also use SolidWorks under Windows where geforce cards sometimes cause weird problems.