[TJ Clark]

My question is, Do these batteries need to be "Starting batteries" High amp, short draw period?  Should they be Deep Cycle Batteries, low amp, long draw period?

Do I really need 6 Batteries?  Could 3 be enough with a good quality deep cycle battery?

These agm batteries (O'Rielly) are only 3 years old, maybe I should just put in sealed lead acid batteries.  Seems about the same life expectancy at half the price.

The Guru's Expertise is greatly appreciated!!

IMO you want lithium, if not then a good deep cycle AGM like the Lifeline 8d AGM's. 

Good AGM's and Cheep LIPO4 are about the same cost these days. The LIPO4 cab survive nicely on the same charge settings as the AGM's but a little tweaking to set points available in most inverter chargers and shorten charge time.