extra TLD's are nice, but remember that requires extra marketing and work on the part of your SEO. Pagerank will start at ZERO for each domain until you build a reputation and have people linking to your domain (this is true aslo of the subdomain method you were thinking about).

MOST places will put domain.com/fr/ or domain.com/de/ when it comes to language options as this will at least let the pagerank and recognition in google to trickle down to your folders.

Goinw with subdomain or with new domains means you must market each one and you become a small fish in a big bowl. Using an existing domain allows you to keep the rank you've already gained, and then just add more on top of it.