Hi Atte,
I can confirm that you should easily get <10ms latency with a modern USB card.
I have an i5 laptop (Asus UL30JT), so slightly less powerful than the one you spotted. My first experiences on it were with the Edirol UA-25 (the old model, not the EX one). That's USB 1. Jack would start at 8ms and be plainly usable with Ardour: 4-5 tracks, some plugins on each.
Then I tried a Scarlett 2i4 for a couple of days. It's USB 2. Jack would start at ridiculously low latencies, like 2ms or so. But working with the same Ardour sessions was still only possible at 8ms. So I figure the bottleneck is my CPU rather than USB. I brought the card back anyway.
Eventually, I opted for the Komplete Audio 6. This could fit your minimal requirements of "4in (2 of these should be phantom power) + 4out". Latency is the same as with the Scarlett: Jack starts very low, but for what I'm doing, with an i5 CPU, 8ms is the most reasonable choice. I find it's a very good soundcard, very clean preamps, it works out of the box on Linux. So if you end up looking for a USB card, you could consider that one.
A note on the Lenovo U310 which you spotted: it has 2 x USB 3 and 1 x USB 2. This looks good because it could mean that the USB 2 slot is not on an internal combo (as is the case with some other laptops, mine included). It should be better for latency, and possibly diminish the risk of noise interferences. You may however be restricted to using that slot for the soundcard, as USB 2 devices are not guaranteed to work on a USB 3 slot.