When I bought my Deka ETX14, the seller told me the optimate 6 was OKish. According to him, it is the only charger from optimate lineup that is enough for the Deka battery. He did not tell me why although it is a 5A charger which seams... well OKish for the DEKA.
That seller told me I'd better go for a Fronius Easy1206 which is a 6A charger.