I’m not going to make any mods for a first time. I need it to be silent as much as possible just out of the box.
Ok, you have to be more careful cherry picking your parts.
1) CPU: Intel Core i5 2500. I'm not going to overclock it or maybe just a bit up to 3.5 GHz but not more.
So you mean the 2500K, not the 2500, don't you?
2) CPU Cooler: have no idea. As I know there is back compatibility between LGA1155 and LGA1156 so I completely trust your experience. Please advise me something really quiet.
Haven't you give any read to SPCR Recommended charts? The CoolerMaster Hyper212+ WHEN DOWNVOLTED gives you the most bang for the buck. Swapping a fan could be called a mod? Then the Noctua NH-C14 gives you one of the most silent out of the box experience and it's a top dog: unfortunately it costs three times the above mentioned CM. In the between, several Scythes may serve you very well (give a look to Yasya or Mugen B).
3) Motherboard: don't care. It must have USB 3.0 and SATA III support and maybe RAID. Not sure about the last one. It depends on what I'll prefer in future: RAID or NAS.
There's no recommendation to care about, as Sandy Bridge isn't yet in the wild.
4) Case: I can't make a decision between Antec Solo and CM Sileo 500. I really need your advice here! I know that most of people here more or less are fans of Antec, so I will glad to hear something about Sileo also. I give some priority to Antec, but need to hear other opinions also.
I own the Solo and love it, but the CM is a great solution for casual silencers: if it's cheaper (here it is) than the Solo, you may comfortably opt for it, but you lose the drive suspensions. Besides they share almost the same limitations, essentially a low airflow, so they're not best suited for high power game stations (but it's not your case, I mean).
5) PSU: another dilemma is here. Corsair vx450w or CM Silent Pro 500. Which one is more silent? Your pro et contra? Or maybe something else?
Something else: give a look to SPCR charts, please.
However, the VX450 is now made by CWT AND IT REALLY SUCKS with reference to quietness. Avoid like the plague.
6) Memory: 2x 4GB 1333 or 1600MHz. I told you before that there will be virtual machine on my system so there is no too much memory. Please advice about frequency and about radiator and about vendors. If I buy 1600 MHz memory how I can manage it to work?
For a good all around, you may look for Kingston HyperX 1600MHz, but 8GB if you have a 64bit OS (4GB on the contrary) if you work with VMs.
However, several motherboard manufacturers publish an HCL for their products: if in case, stick with it for brand/speed.
7) HDD: Western Digital WD6402AAEX. Just one for beginning
It's probably the worst choice for the CM Sileo, and I would avoid it at any rate.
If you need that size, go for something like a ST9750420AS, the Seagate Momentus 750GB: at least, if you "need it to be silent as much as possible just out of the box".