Need advice for a Engineering desktop ~500€

Unless you need that optical drive there's little reason to include it. I'm also not very sure about the quality of that power supply. As for video card, that depends if you'll do anything that requires 3D rendering. If not, then no you don't really need one. I'd also recommend getting a 16GB kit of RAM seeing as you'll need to have many programs open at once.

If you provide country of residence/the online shop you'll be buying from I can check if there's anything better.

Cheapest decent unit I could find is this: http://www.pccomponentes.com/seasonic_s12ii_520w_80_plus_bronze.html

It's a bit more expensive but it's a good PSU (as good as you can get at those prices anyway). You could go with the Enermax one but it would affect the longevity of your components.

Simple advice
Delete the CPU cooler, the standard one is fine.
Buy a cheaper case - 40 euro is plenty
Now you can afford to buy an i5 4460, which is much more powerful and better value for money.

I don't know if all of these parts are available in your country, but here is a list I put together for around that price. If you cant find all of these parts, then take things around that price that you CAN find, just make sure to check the ratings to see if its good or not. (Just don't go with an EVGA power supply.)

PCPartPicker part list: http://pcpartpicker.com/p/MVWCGX
Price breakdown by merchant: http://pcpartpicker.com/p/MVWCGX/by_merchant/

CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor ($174.89 @ OutletPC)
CPU Cooler: Cooler Master Hyper TX3 54.8 CFM Sleeve Bearing CPU Cooler ($18.73 @ OutletPC)
Motherboard: MSI H81M-P33 Micro ATX LGA1150 Motherboard ($45.89 @ OutletPC)
Memory: Mushkin Stealth 16GB (2 x 8GB) DDR3-1600 Memory ($59.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($45.88 @ OutletPC)
Video Card: EVGA GeForce GTX 750 Ti 2GB Superclocked Video Card ($99.99 @ Newegg)
Case: Cougar Spike MicroATX Mini Tower Case ($33.99 @ SuperBiiz)
Power Supply: Corsair CX 430W 80+ Bronze Certified Semi-Modular ATX Power Supply ($40.98 @ Newegg)
Optical Drive: LG GH24NSC0 DVD/CD Writer ($13.89 @ OutletPC)
Total: $534.23
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-01-17 13:36 EST-0500

500 Euros = About 545 USD

If you'd let the i5 4590 fit into your budget, it's a better option than the i5 4460.

Angel8,

Engineering uses such as Matlab and simulation are so calculation intensive, with a moderate cost, there are advantages to buying and upgrading a used, high quality workstation that was designed for that purpose and then upgrading it. Several months ago a friend asked that I suggest a system to run flight dynamics problems in Matlab (von Karman turbulence) and that system would have cost nearly $7,000. Matlab can be fully multi-threaded so there are extreme advantages to having as many cores as possible.

Last February I bought for $190 including shipping:

Dell Precision T5500 (2011) (Original): Xeon E5620 quad core @ 2.4 / 2.6 GHz > 6GB DDR3 ECC Reg 1333 > Quadro FX 580 (512MB) > Dell PERC 6/i SAS /SATA controller > Seagate Cheetah 15K 146GB > Windows 7 Professional 64-bit
[ Passmark system rating = 1479 / CPU = 4067 / 2D= 520 / 3D= 311 / Mem= 1473 / Disk= 1208]

These are beautifully made with server quality components that are designed for long sessions under full load. > Extremely reliable

This system was usable as received and I gradually upgraded it, purchasing used CPU's and also using several parts which were taken from my first system when I changed them:

CPU1: $230
CPU2: $170
CPU motherboard .memory/ fan riser: $75
Memory: 48GB: $180
PERC H310 RAID controller: $60 (converts disk from 3GB/s to 6Gb/s
GPU: on shelf from other upgrade
SSD: on shelf from other upgrade
HD: on shelf from other upgrade

And the results were very good:

Dell Precision T5500 (2011) (Revised)> 2X Xeon X5680 six -core @ 3.33 / 3.6GHz, 48GB DDR3 ECC 1333 > Quadro K2200 (4GB ) > PERC H310 / Samsung 840 250GB / WD RE4 Enterprise 1TB > M-Audio 192 sound card > 875W PSU > Windows 7 Professional 64> HP 2711x (1920 X 1080)
[ Passmark system rating = 3844 / CPU = 15047 / 2D= 662 / 3D= 3500 / Mem= 1785 / Disk= 2649] (12.30.15)

That's therefore a 12 core / 24 thread system running at 3.33 /3.6GHz with 48GB of RAM, a 250GB SSD and 1TB enterprise level HD and a very good 3D performance, spending about $900 with about $400 in other parts I already had.

My current Project:

Purchased for $53 + 25 shipping:

Dell Precision T3500 (2011) (Original) > Xeon four-core@ 2.8 / 3.06GHz > 4GB DDR3-1333 ECC (2X 2GB) > GeForce 9800 GT > 500 GB
[ Passmark system rating = 1962, CPU = 4482 / 2D= 609/ 3D=805 / Mem= 1408 / Disk=972]

CPU: $60
RAM: $43
GPU: on shelf from other upgrade
PERC 6/i RAID controller: on shelf from other upgrade (was in the T5500 when I bought it
HD's: on shelf from other upgrade

Total= $185 or with the value of used parts about $350

Precision T3500 (2011) (Rev 2) Xeon X5677 4-core @ 3.47 /3.73GHz > 12GB (6X 2GB) DDR3-1333 ECC > Quadro 4000 (2GB) > PERC 6/i +Seagate ST3300657SS + WD Black 500GB > Windows 7 Professional 64-bit
[Passmark system rating = 2751, CPU = 7236 / 2D= 658 / 3D=2020 / Mem= 1875 / Disk=1221]

For example you could buy something like:

COMPUTER WORKSTATION DELL PRECISION T5500 QUAD XEON 2.0GHZ 6GB 320G QUADRO 580 sold for 157,00 EUR + 35,00 EUR shipping (Italia)

http://www.ebay.es/itm/COMPUTER-WORKSTATION-DELL-PRECISION-T5500-QUAD-XEON-2-0GHZ-6GB-320G-QUADRO-580-/201478390748?hash=item2ee90c43dc:g:ET0AAOSwwE5WV2ae

The CPU is a bit slow but that system is not far from being usable. There are many excellent LGA1366 CPU's up to the Xeon X5690 6-core @ 3.47 /3.73GHz. Buy a strong 6-core CPU , 3X 8GB of PC3-10600R RAM (DDR3-1333 ECC Registered) and a good SSD- Samsung 850 Evo 250GB. Later, add a 6GB/s RAID controller, a second CPU and more RAM.

The advantage to this idea is to have a system up and running while it is improved- only apart a couple of hours at the most. Also, as it can have two 6-core CPU's and 92GB of RAM, the potential can be very high.

Cheers,

BambiBoom

HP z420 (2015) > Xeon E5-1660 v2 six-core @ 3.7 / 4.0GHz > 32GB DDR3 ECC 1866 RAM > Quadro K4200 (4GB) > Intel 730 480GB (9SSDSC2BP480G4R5) > Western Digital Black WD1003FZEX 1TB> M-Audio 192 sound card > 600W PSU> Logitech z2300 > 2X Dell Ultrasharp U2715H (2560 X 1440) > Windows 7 Professional 64 >
[ Passmark Rating = 5064 > CPU= 13989 / 2D= 819 / 3D= 4596 / Mem= 2772 / Disk= 4555] [Cinebench R15 > CPU = 1014 OpenGL= 126.59 FPS] 7.8.15

If you can stretch your budget a bit more, get the same CPU and motherboard as me (see signature) - with a bit of luck you should be able to run at over 4GHz on the stock cooler like I do, which is very very good value for money.
I am running 1.15V Vcore; more than this caused core temperature to go too high with stock cooler.