As set ups go, you are probably okay especially given that you don't have room for more batteries anyway. There's a whole bunch of gadgets and enhancers you could throw money at (ACR's, monitors, inverters super whoppdie quick charge gizmo's etc) but for basic cruising you don't need them.
Well, you might want an inverter - I have a 100w and 300w that use 12v plugs, they are suitable for low power appliances (tv, laptop etc..) and a 700w that alligator clips to the battery terminals that I've never actually needed to use (yet). 54 bucks at WM, just in case the Admiral decides she really needs the hairdryer (600w version) is worth it.
Everstart batteries are made for Walmart by Excide or Delphi; the deep cycles by Delphi. Assuming yours at 115ah are in fact deep cycle they go for mid-60's or so each. If you really want to spend some money replace them with AGM's instead of lead acid, but only if your current charger will handle AGM's charge rates. When replacing them make sure the new ones will fit and try to match them up. You don't really need 'dual purpose' and all the start/house stuff because that little Yannie isn't a diesel truck motor any deep cycle can handle it (purists can now start hissing in the back ground) Just don't crank the motor for more than the 5 seconds it should take to start it.
Do carry a generic jump starter (40 bucks from walmart) as a just in case. They make good ones with air compressors etc.. built in for a couple bucks more.
If you can find the room for even one more battery, make another bank and double up the bank you currently have as a 230ah bank - your batteries won't cycle as much.
Now if you really want to spend some money, get a motorcycle starting battery and make it bank 1, just for starting - that little Yanmar doesn't need much. The batteries are small and can fit anywhere you can run the proper wire size to it. Then wire your two current batteries into a single bank, more ah's per bank prevent cycling.
There's a couple ideas for throwing money at - if they don't work PM me and I'll send you my paypal number