A full load (as 4 Prime 95 instances) would be around 115W AC*, I guess.

(* under verification)

Not a chance unless you're assuming a very inefficient power supply.
You'd need 8 instances on a faster CPU plus Furmark to get close to 115W DC.

Right now, of course: but there are also SSDs.

Yeah, which is why I'm saying the ideal board depends on the planned upgrades.
A basic SSD has little use for SATA3 and accelerates lots of operations spectacularly on SATA2. But if you plan on buying an expensive SSD for its monster throughput...

at least in Holland, the difference between H67 and H77 intel board is now about 10 euros. So I've decided to go with the latest one, presumably also being a bit more efficient (no controller for conventional PCI, no separate USB3 controller).

w.r.t. server board. Ideally, yes. But the price to pay is higher, and reuse-ability of the HW in my home park of machines is lower. So for now, I think what I'm going to build is a good compromise between price and performance for a given task.

I've considered SSD as well, but it's just does not justify its price (for now). If I'll be seeing high traffic to my machine, I will first look at ways of caching webpages in RAM, which is certainly cheaper, and only if it's really not able to manage, will go for SSD.

The price difference is a bit higher here. But the real difference is that you can buy the old boards on the used market.

You might also have to face bleeding edge issues with one of the newer boards. Plus no USB3 until you upgrade the CPU apparently. But none of these are deal-breakers I think.

It's not that an H77 board would be a bad buy of course. It's just that it's not the very best value. If you're not an obsessive optimizer, that's OK.

edit:
You don't really need an SSD for a web server on a small pipe, no. There are cheaper solution if RAM isn't enough.
Having a drive with a monster throughput is only useful if you have a monster pipe to back it up. Got fiber?

fiber is probably coming somewhere next year

what would be a better value board in your opinion? Previous generation H61 or H67 based?

Or maybe not even an Intel board...
Among Intel boards, I think the DH61AG is the best value low-power board (how much would you pay for that pico?).
But looking only at H67 vs H77, even saving only 10 euros makes for better value.

I own D945JSET board which is currently used in a little computer based player. It has similar 12V input, which is nice, but other things drove me crazy: notebook memory, notebook ata connector, etc. In the end, I found what to use it for, but I will hardly use that board for anything else anymore. So for me that was a lesson learned: I better go for a normal miniATX board, which I can later put in another machine, exchange components, etc. And that brings value for me, and (i think) drives total maintenance cost down.

But if I had money to spare, I would go for special boards, in the end, it's hobby, and it should also be fun

I didn't realize (or forgot) you wanted such a large board. I've not build anything like that in years and I use laptop RAM more often than not now.

Notebook storage connectors died with IDE. The connectors are the same.

ok, good to know.

w.r.t. picoPSU: I'm still a bit in doubt if I should go for it, or just install good 80+ 300W PSU and that's it. A conventional PSU has certainly advantages, such as more power connectors. Also, I'm a bit in doubt if picoPSU is as reliable. After all, it needs to run 24/7, so I want be sure that it won't put my house on fire

A so-called 80+ PSU won't be close to 80+ with that power draw unless you pick a really good (and expensive) one. Once again, ratings are deceptive...

btw, Mini-box picoPSU 90 + 80W Adapter Power Kit | PICOPSU-90-80W = ~55 euro,
be quiet 80+ 300W PSU = ~40

I don't understand. Why don't you order your pico from Logicsupply?
Note that you can resuse an existing adapter. Lots of people have spare adapters they could give you if you don't have a compatible model.

That Bequiet may be more reliable than a pico and would certainly give more room for upgrades... but otherwise it's probably crappy. It depends what your priorities are I guess.
If I didn't need the most quiet PSU, I wouldn't buy anything worse than a Superflower Golden Green.

logic supply is more expensive. What difference does it make, do you think the one I mentioned can be a fake?

Logicsupply is cheaper (like EUR 30-ish) if you don't buy unnecessary accessories. Have you looked at the European site?
I'd rather deal with them. Even if you don't buy a knockoff, you can have a problem. Since there's no serious corporation backing the product, you'll be glad to have bought from a knowledgable and dependable retailer.

yes, European.
I also have trust in my local retailer...