My advice would be to not even think about adding less than 8GB of ram to your machine - 4GB is insufficient for a smooth workflow in InDesign and General graphic design. In Windows 8GB is also a minimum for anything but Office work.
16GB is preferred.
As for those systems you mentioned:
- Dell OptiPlex 3030 All-in-One: AVOID! Just a bad idea. Not suitable for InDesign work. Screen res is too low, and expandability is zero. This machine is meant for classroom use, not for real work. And with "classroom use" I mean classes in Office products, or for secondary school use.
- Dell OptiPlex 3020 micro PC: AVOID! Those machines only support up to 4GB, and are again hard to expand. These are typical Office machines.
- Dell inspiron 3646: Again AVOID! Again this machine cannot be upgraded to 8GB, and only supports up to 4gb.
Also, all of these machines sport an Intel HD graphics chip that leeches valuable system memory, which results in even less memory for the OS and InDesign. These systems are all wrong for InDesign, and cannot be expanded or improved easily in the future.
8000kr means you have about 1100 dollars to spend. For that kind of money you can do much better.
I built a system for you at http://www.misco.se/
Intel Core i5-4670K, 3.4GHz, Box, 6MB, S-1150: 2074
sapphire Radeon R7 250 1GB: 763
ASUS B85-PRO GAMER - motherboard - ATX - LGA1150 Socket: 976
Crucial memory - 8 GB - DIMM 240-pin - DDR3: 709
Cooler Master Thunder 600W - nätaggregat - 600 Watt: 489
Seagate Barracuda ST1000DM003 7200rpm - 1 TB - SATA-600: 574
case: Coolermaster haf nine one two: 768
Microsoft Windows 8.1 64-bit OEM DVD Swedish: 943
Dell P2014H - LED-skärm - 20" – IPS-panel 1600x900: 1124
total: kr8420
It is slightly over budget, but still manageable, I think. This is a fast machine, with ample space and expandability - FAR beyond the aforementioned machines. A future-proof setup that will last you long - investing less money in a sub-standard machine (like the ones you mentioned above) is generally a very bad idea, since that hardware will only last you a short time. I chose high quality components. Later you could expand this system with more hard drives, an SSD, and so on.
InDesign will work very well on this. As will Photoshop, Illustrator, etc.
This setup includes a high-quality pivot-able IPS screen (IPS is the minimum for a quality graphic design screen) - not too big, but you mentioned you will have more money later, which you could invest in a second larger IPS screen, and connect to this rig, so you will have two monitors to work on - something you would NOT be able to do with those other cheap rigs.
The only caveat: you would either have to build the machine yourself, or get someone to build it for you. Misco might also do that, but at extra expense. Perhaps ask a nephew or other family member who knows his/her way around computer hardware? ;-)
PS the forum chokes on the number nine one two?