Help with multi stage battery chargers, whats best and whats not?

Hi all
I am looking at multi stage battery chargers and its hard to compare them.
Does any have experience or knoledge to shed some light on whats is required please?
I am running lead acid type batteries of different types with an independant charge system.
I currently have a dual 12v power supply (that will run eva cool from 240v/ that is also a 10 amp regulated battery charger (these units are no longer available as a combo unit for some reason?) The unit does well when batteries are new ie it charges well and then tuns off when battery is full, however once the battery is over a year old , but still working well, the charger does not reconise it as being full and will keep charging the battery and it then looses liquid rapidly.
Is a 3 stage charger what i require?
I like the 10 amp capacity as gives me a good chance to top up the aux battery if having an overnight stop with 240v available.
I saw some "min kota" chargers advertised (same brand as 12 v outboard motors) which have a 5amp 3 stage unit with 2 outputs which sounds good for when vehical was not in use and could set up with one output per battery.
Could the 2 x 5amp be directede to one battery ie the aux for faster charge over night?
I wish the unit to be permanently mounted on the cargo barier so size / weight is somewhat important too.
Sorry its a bit long winded but i needed to supply details of the situation i fel for a decent reply.
Kind regards
GN