In reply to Caralynh:
I climbed a 5500m mountain in Peru in 2011. We climbed our route, from a high camp in a round trip. I wore Spantiks, whilst my partner wore Phantom Lites (the old version of Phantom guides).
Although we both had slightly cold feet, on occasion, during our climb, we were both fine in our choice of boots. I thought the Spantiks were a bit OTT and would probably wear something a little less bulky if going again.
Although I probably would have been fine, I wouldn't risk using conventional leather boots like Nepal Extremes or your SM Lites.
In the area we climbed we thought the temperatures were a fair bit colder than the Alps in summer, but the glaciers were much, much smaller than those in the Alps.
Rock and Run are selling Scarpa Omegas for £99 atm. I used to have a pair of these boots and found them excellent. I would be happy wearing them on the route I did in Peru, with a good gaiter like a Outdoor Research Crocodile.
We found day time temps to be pretty warm (thermal top and a pertex windproof) and generally dry underfoot. I would recommend taking a pair of light trail running/fell shoes for wearing below the snow line.
Drop me a PM if you want any more info and I'll do what I can to help.
HTH