La Sportiva boots rock
I have had three different mountaineering boot selections from La Sportiva in the past ( the K3- no longer available, the Nepal Extreme- more suited to vertical ice, and the Makalu- the pair that I'd recommend for you), and I have been very impressed with each in their respective performance niches. I wore the Makalus for many extended trips in warmer weather with moderately heavy packs (25-40 lbs), and they provided great support and durability. I also used them on a few winter trips, and they proved to be stiff enough to handle moderately steep snow and ice for general mountaineering, but I wouldn't climb steep ice in them.
A few words of warning for you before choosing any boot:
*Shopping online is very convenient and probably the easiest way to get great prices on some products, but it is imperative that when buying a more technical mountaineering boot (or any boot for that matter) you take time to go into a shop and get properly fitted in the boot first. A good shop should measure your feet, match boots to your foot volume, length, width, and foot spread, and will be patient with you as you try them on a boot ramp and walk in them.
*Although I recommend the Makalus, they may not work for you. The Maks are a narrow to med width boot with a relatively low volume (good for my long skinny feet). If your feet are wide or high volume, you may want to consider Limmer, Garmont, Vasque, or Asolo. Buy boots for fit and comfort above all other factors, and your feet will thank you.
Happy hunting!
-C