I liked the Cambridge YC HQ quite a bit. It's much homier than the one in MV.
Luckily for YC, it seems all they need to do to get setup is buy a place and get their architect to make it perdy.
Fortunately we can expand in time if constrained in space: just have multiple dinners per week. That would get us 7x without needing to find a new building. I've had my eye out for places in Cambridge, but it would be really hard to beat the current one.