Only thing I can tell you is...this distance is critical and honestly at 6'4" you could probably stand to be even more stretched out.
I am 6'1" and ride 600mm from saddle tip to handlebar center. Many pro's ride 625mm for my size and even more stretched out.
Measure your current bike and let me know what it measures....mm's or inches.
Don't settle for a bike you can't set up to generate power. Comfort actually comes for many by getting leaned over a bit, rotating pelvis forward and stetching out. Also good posture on the bike which is a function of proper pelvis tilt requires more reach. Riding cramped is no good for power or comfort.
Don't settle for a bike that doesn't fit perfectly. 2 hours + in the same position...its pretty important to get your balance and contact pts points right.
Last edited by Campag4life; 03-15-14 at 04:40 PM.