I'm currently using the Optima 34M which I think may be too small for electronics and cranking (although it's worked well so far).  I'd go with the Delco Voyager, but there aren't any dealers around here.  Matter of fact, I'm really limited in what I can buy and where.  I need at least a group 27.  Any suggestions?

If you have a Sears or Kmart around get a

Die Hard Platinum Model group 34 or 31, the 34 has 880 CCA and the 31 has 1150 CCA. 

Here is a link:

http://www.sears.com/shc/s/p_10153_12605_02850131000P?prdNo=1&blockNo=1&blockType=L1

They are awesome batteries, and will be on my boat next time I have to replace a battery.  Made by Odyssey for Sears.  If replacing an existing group 27 than get the height adapter from Odyssey.  See specs below

http://www.odysseyfactory.com/marinespecs.html

I've been running a big Interstate for the last couple of years .... has worked real well. Runs 2 HDS systems, LSS1, and starts. Come on up here to Murray to the Interstate outlet.

More brain wash.

Stick with a high quality group 27 or 31 dual purpose. It would take the Odyssey 31M-PC2150 to come close to matching them @ about twice the cost.

I run the white marine crank 875 cca from O'Reilly Auto Parts.  It is about $85 and keeps my hd units going and starts my Opti in all kinds of weather.