I'll offer additional advice, however, I'm preparing for an office move so I'll be to the point now that additional hardware spec are available. And, please do not apologize for your native language and English skills - you're conversing quite well in a non-native language FWIW.
First, the brief IMHO not-so-good news - I would upgrade, either to a newer Windows PC or to a newer iMac, and I
would not invest any more money in your current PC. Your current PC is an older, mid-range (in 2012) PC that was not designed for use as a CAD or production machine - in my office, I would call your PC a "door stop" as in the only task we would use it for is to hold open a door; I am not being disrespectful here - renders that are taking your PC 20-30 minutes would likely take 2-3 minutes (maximum) on a newer, optimized PC or iMac.
Now that I've looked over the specs a bit more, you're using a mid-range Ivy Bridge processor that was designed in 2011 and available in 2012, and the i5-3570K was barely an improvement over its predecessor from 2 years earlier - and there aren't any decent newer i7 processors that I'm aware of that will fit into Intel's LGA1155 socket - Intel moved on with the newer architectures a couple of years ago. You'd be spending US$350+ to update your processor in a PC that wouldn't really take advantage of the new speed.
RAM. You're using 8GB, and I'm now guessing that you're using a 32-bit version of Windows. More RAM really won't help you here as the OS won't take advantage of more than 4GB of RAM and then the OS will be looking for HD space for RAM swap space, which really bogs down the speed of your PC. We run our CAD apps in Windows 8 or 10 Pro, the 64-bit editions, and our apps can use as much RAM that's available.
Hard drives. I love the Black, and I love most Intel SSDs - but (again, IMHO) using the HD by itself and a tiny SSD is not the choice in my office or pretty much anyone I know. Spinner HDs go in the PCs that use MS Office - our production PCs use only PCIe SSDs now; I started out with SCSI drives in the late-80s and there's no way I'd go back to spinners in my production PCs or Macs. We use Black drives in some of our archival machine and NAS boxes (in a room that has a door we can shut, as they are a bit, um, noisy...).
You don't need a top-of-the-line PC or Mac, but a newer PC/Mac will go a long way to spending less time waiting for your work to complete. Suggestions are to read up on Graphisoft's web portal a few things that may offer some insight (sorry, I bookmark only the English-language information):
http://helpcenter.graphisoft.com/technotes/setup/software-technologies/virtual-memory-usage/
http://helpcenter.graphisoft.com/technotes/setup/software-technologies/multiprocessing-and-archicad/
http://www.archicad.co.nz/support/support-options/system-requirements - note that they recommend only 64-bit OSes.
Last bit, your choice of video card is likely also bogging down your work. It's an ASUS-branded Nvidia "gamer" card - gamer video cards are not optimized for CAD/3D/rendering work. Do take a look at Grapisoft's recommendations for video cards:
http://helpcenter.graphisoft.com/technotes/video-cards/recommended-video-cards-for-archicad-19/ - we only use higher-end Quadro cards, but they're expensive; at least make sure your video drivers are updated!
Keep in mind that Apple offers refurbished Macs in a special store (start with refurb.me - they have country-specific web sites, and it's just a front end for Apple's web portal). If Apple does offer new Macs soon, then the current iMacs will get marked down as well! Cheers!
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No question its something that many people are eager to see, but is it enough to justify a mid-cycle refresh?
Financially, for Apple, not likely. Most of the peers I know have completely stopped buying peripherals and PCs without the USB-C port, and I have too. In my aforementioned move, I have a bag that's going to Free Geek - all but two of my Firewire cables are in it, along with some of the older components that are near the end of their warranty (this keeps my bond rates lower too, less risk on me being covered by warranties and not the insurance company...).
FWIW, I'm also not keen on Rev. 0 Macs, having not good experience over time. I'm hoping that their experience with the new Macbook and its recent update plus PC makers experience with the new TB3/USB-C hardware/ports will make the refreshes of rMBPs and iMacs go a bit smoother. I still recall my stepping off an underwater shelf on my qualifying diving trip in 1989 - I let others go first now, and I'm sure Apple's taking note with the newer ports/chipsets as well!