New
#11
I see that the G3420 has a tdp of 53 watts, so unless you add a graphics card you should be ok . The ram uses very little, and onboard graphics don't use much. Lets hope that the psu is a reasonable make like FSP. If you google the case name you may get some feedback on the installed psu.
Not off the top of my head. It depends on what is available in your location. Your signature indicates you know the good brands. Just a word of warning about small cases - they can overheat particularly if you are in a warm climate without air conditioning. I had an old ACER Aspire desktop which had a small case and ~200W PSU. It used to overheat badly. I recased it for $73 with 450W PSU and it's still running strong and cool even on the hottest days.
Recase an Acer Aspire X1700 X1800 desktop PC
Without a budget then it's all just around and around...........
I'm building a mini-ITX as we discuss your PSU but I'm going for a much different rig, my BitFenix.com case could interest you except I don't know your budget plus better cases rarely come with a quality PSU if offered as a combo one or the other or both are normally sacrificed.
What stores are available to you in Italy it seems you may have the best line on where to shop. Just get a cheap combo with a PSU above 250-300 and you could be right as rain. For me I might skip the combo and just shop the best of both that you can afford.