It's definitely possible to make much more money at lower stakes playing STT's and MTT's than 2nl-10nl. That being said you'll probably find that it's a bad idea because STT's and MTT's require a different skillset than cash.
In other words to beat 25nl it's strongly recommended that you beat 2nl, 5nl, and 10nl for a reasonable sample. The same can be said for 50nl and 100nl. Yes you could sit directly down at 100NL and proceed to grind- but unless you're very gifted you'll probably get waxed for quite a bit of your MTT created BR.