Sounds like now would be a good time to consider going into something a little bigger like a 550 size. My Century Swift NX (550 blades) flies much like my bigger ones and does not cost that much more to get into the air then my good 450's and can be set-up for use with 4S. or 5S or 6S packs.
Since getting my first larger electric heli, I find my 450's now sit on the shelf a lot.
You will find many threads about it and other larger helis in this other electric forum here on RCG that is dedicated to larger electric helicopters (those larger then 450's)