Hi Zipperdoyle,
Have you ever thought of doing the Guanacos Route (Upper Valley). In my opinion it is a better and safer route. No crowds and the route is a bit longer so the acclimatization schedule is better. This route also has a higher success rate. If you're interested in that route I'd have to recommend Natural High Alpine Adventures http://www.naturalhighalpine.com/trips/aconcagua.shtml But I've got to say I'm a bit biased as I'm owner and guide for the company! I have done many successful climbs of Aconcagua via this route. Take care.