I'd go for it if the team is good. With 20 senior people, that's a lot of possible mentors and people to learn stuff from. The money is obviously good, and it's the thing you want to be working on.

You can evangelize once you're there. Or, you'll find out that what they're doing is actually best for the environment they have. I seem to remember SVN handles larger repos better.

Don't work about being "junior." I joined my employer as new college graduate, and still was able to influence some changes in my environment. However, I still use RCS for some scenarios because it works best in my environment.