That size of codebase is definitely an issue :) Last time I had 500k of C#+C++ (5 years ago roughly), I split the solution into around 20 solutions, and used binary dependencies (with CruiseControl.Net on top of that [1]).

I remember reading similar advices in other places as well (and for other languages/platforms, too).

[1] http://mikebroberts.files.wordpress.com/2007/01/enterprise-c...