Is it?
I’m planning a 3rd person action/adventure game for windows pc; (with much adventure an few action).
these are my other’s pc specs:
cpu athlon x4 631
gpu 8800gt
ram 8gb
According to unity system requirements it is; but I read some advices in this same forum about upgrading systems more powerful than mine; so a specific advice would be appreciated.
also: Am I going to have issues not having dx 11 support on my gpu?
i work on a intel hd 3000, so go figure ehehehehe
I have ran Unity (I think 3x at the time) on an old desktop with an integrated like… intel 8xx (pre-945gm) el crappo video card - no problems. As long as your game is not super graphics intensive then don’t worry about it. But then again if your planning on using any fancy like DX11 specific features, I suppose then in that case you would absolutely require something newer and more powerful. And also if you have poorly optimized textures, and/or shaders, that will also bring an old rig to its knees quick. Heck instantiate and destroy stuff rapidly can wreck even the newest of rigs, so it really has a lot to do with optimization and testing.
thanks for the answers; I have also the possibility to get a gtx 460 for very cheap; would it worth it or performance between 8800gt and gtx 460 is similar?
The question could also be, " Is this bucket big enough to fill with water" It all depends on the size of the bucket and the amount of water you want to fill it with.
So, if what you say is that unity says your system is good enough, it might be, very much depends on how you make the game.
If you manage to make the game on your current specs, you are going to be able to sell/give the game to a broader user base.
If you consider upgrading your system, you might be able to make a more advanced game, or not have to figure out as much optimisations to achiveve same results.
There are too many variables to think of, to be able to give a good response on your question.
My advice, start making the game, if you along the way notice the hardware isnt enough. Then upgrade the hardware when you need to.
Or if you feel you want to upgrade the rig anyways, then do it.
But save the old hardware, and you will be able to test it later on to see if you actually managed to make the game work on the older hardware aswell.
Unless it’s another engine people seem to talk about, then you need quad titans just to open the file menu. Fine, I’ll stop joking now… kinda 
Thank you all for the advices; I’ll begin with the hardware that I already have then we’ll see.