My DH has those Pearl Izumi boots too, and raves about them! He says that they were money well spent.

I have the same problem with winter boots and booties not fastening tightly enough around my calves. I've taken to wear low softshell gaiters over my Sidi boots in order to get a nice tight seal at the ankle.

I bought a pair of XStatic sock liners at EMS, and they have made such a huge difference in how comfortable my feet feel. It's not just the wicking capabilities (been wearing sock liners for years), but something about these particular ones actually makes me feel warmer. Add a pair of smartwool socks and my Sidi boots and I'm good for a couple of hours.