I'm not an electronics technician however i can say that the device will only draw what it needs from the power source so if it needs 1.5A to function and the source is capable of delivering more, say 5A, there is no problem. But if it needs 1.5A and the source can only deliver 1A then there is a problem. So if you're asking will there be a problem with the nuvi if you can boost the GTM25's current output to 2A, then absolutely no there won't be provided that also voltage is maintained at ~5V only.