So far I have been looking at:
Eureka Alpenlite 2XT
GoLite Utopia 2
REI Arete ASL 2
I am a little concerned about wind and the Utopia since its only a shelter. During the winter I dont see this as a problem for I can just pile snow on the edges but during summer I am not so sure.
Speaking from experience there's a couple of pieces of advice I could give you..
1) Piling snow around the edges works fine in winter - unless you're bare and exposed where it only blows away (or worse, in..)
2) You said "your girlfriend and your brother" - and all those tents are two person or two+ person. If three of you are going, I'd have a 3+ or 4 person tent, or two twos. When I go out in winter with a generous three person tent with two people it's cramped. you often need room for gear and stuff - particulary if the weather is nasty.
3) You're talking about "in winter.. but in summer" - don't use a four season tent in summer. if they're right to take a snow load in winter, they're heavy, and hot, in the summer. if you don't want it to take a snow load, don't buy a four season tent at all.
4) I hope it's not your girlfriend and brother's first hiking experience - if it is, have mercy on them and take them out in the regular season first before doing the seriously hardcore stuff in winter