Unless you're router is pretty old, as in has something like a 10Mb/s WAN port you'd be stuck at download speeds around 7-8Mb/s. Other than that, above poster nailed it.
I use to have router with very limited WAN port, but was bought a long time ago by someone else and didn't realize it. Went 2 years at 8Mb/s speeds - bricked my router, now at 25Mb/s down.
OH BOY ON ME