so here's my final thoughts on the subject, hopefully will help someone else make up their mind too
between "smart" automatic systems:
National Luna and IBS are similarly priced and the IBS seems to have maybe a couple more bells and whistles. The National Luna Kit does come very complete though as far as pieces parts you need. However, the National Luna's continuous amp rating just isn't competitive with the rest of these systems. If I had the money, I'd get the IBS system no questions asked - I just couldn't justify spending that much money for bells and whistles.
between "less-smart", but still automatic systems:
Hellroaring's BIC, Marinco's VSR, Blue Sea's ACR, Painless', and Redarc's system all work pretty much the same from my reading. The exception being that Hellroaring's system is completely digital, but may be loosing some voltage in the form of heat. I couldn't find any reason specifically that the Hellroaring setup was better than a quality constant-duty solenoid based setup. The Redarc is heavily uses in AU, but I couldn't even find a place selling it direct in the US. The Marinco 710-300A
and Blue Sea PN 7622
are almost identical in features, with the Blue Sea having higher current ratings and coming with the remote switch.
The only other consideration for me was the Power-Gate perfect switch. It's amazing from an engineering standpoint, as it's solid state with none of the downsides and all of the upsides usually associated with solid state devices. Their marketing sucks, their prices are kinda high - meaning it's priced in the same place as the "smart" bells & whistles systems, but without any of the bells.
So in the end I'm going to order the Blue Sea ACR, because it's the cheapest yet hast the best ratings within it's class, and Blue Sea is known for other quality products. They also seem to be US-based, not sure where their stuff is manufactured.
Blue Sea PN 7622 - ML-Series Heavy Duty Automatic Charging Relay
500 Amp continuous rating
Dual voltage sensing
Silver alloy contacts
Manual switch as well as included remote switch
more technical info...
I found it for $150 to $175. I intend to add two battery monitoring LED's (one for each battery) at a cost of $29. So I'm looking at ~$180 for a nice relatively-simple system, with manual and remote control as well as some monitoring capability. The 500A continuous rating is overkill by far, but better to over-engineer than push the limits of a system. I'm lacking the intelligence to turn off "linking" of the 2 batteries automatically after a pre-set time, and lacking any sort of beeper or buzzer reminder that they are linked. For a $200 savings over the IBS system, I can live with that.
I'll also need some new battery terminals, some other lugs, a bit of small gauge wire, (still have the large gauge stuff left from re-locating my main battery), and so the cost will creep up. However, I'd rather continue to use pro-car-audio stuff that I source myself than what comes in any kit.