"The 12AY7 will give you a warmer overdrive but because of it's current draw you'll still be getting a lot of gain. If you want headroom then the 12AT7 would do that as well as brighten the amp up. You might even want to try the 12AU7 as it'll give just clean headroom for the most part."
Sometimes I really like modern pop music. Breathe by Anna Nalick.