Can you do it? Yes, provided you're not cranking the amp to full volume.
Benefits - earlier speaker break-up, if that's what you want
Potential risk - blowing the speaker, which can get expensive.
I use a single G12M greenback with my TA-15. It is rated at 25 watts, but at full-tilt, the TA-15 probably puts out closer to 50 watts, which could potentially blow it. I just never turn the amp up that high, anyway, since I'm mostly using for recording.