Adam, you and I have been emailing back and forth ever since you first joined the forum, and in all that I feel I've gotten to know a little bit about you. I honestly and truly believe that your very best bet when it comes to batteries is to just copy Jeff (Ausf). If he uses 3800 and 4200 nimhs then you should do the same. If you're lucky he'll post a photo of his charger so you'll know exactly what to buy. Jeff's been in this for a very long time and he knows what he's doing. He's not stupid. A little cocky sometimes, but definitely not stupid.
Give his method at least an entire season and then if you think you want to branch out to other batteries you'll be much better prepared. Just follow Jeff's example to the letter and you shouldn't have a single problem, just hours and hours of dependable battery performance with no worries.