Batteries

All I can tell you is what I might do in your predicament.
More than likely I would use what I had for as long as I could, then move on to the true deep cycle battery.
For one thing I don't know the age or condition of the batteries your using now. I have used that type of battery before. I think the name was Stow Away. Bought them a Wal Mart. Even tried some 8D big rig cranking batteries. Nothing like those can compared to the Trojan T-105's. I got 8 years out of a set of 12 T-105's wired in series/parallel for 1320 amphours at 12 volts nominal. Of course I pampered them, not to mention I sized the bank 5 times higher than what I use each night and I would rotate them once a year.

I have to warn you about something on those T-105's though. Those offset terminals will break off. Then you have to drill and tap whats left and be careful not to over tighten the bolt in the soft lead.

Presently I am using 8 Surette S-530's in series/parallel for 1600 amp hours at 12 volts nominal. Which is about 6 times what I use each night. I am shooting for 20 years on these.
The biggest thing to remember is to recharge what was discharged as soon as possible. I sized my PV array to replace what I use each night (plus about 20% more) with one days worth of clear sky sunshine during the Winter months.
Equalizing is very important as well. Any time I go several days* without that sunshine, I always equalize them afterwards. A battery monitor, such as the Bogart 2020 is invaluable. A must have. I am sure you know about the distilled water allready and keeping everything clean, tight, and corrosion free.
If everything is sized right and the region you live in is moderate (no extremes) you can go without a back up generator.

* About 5 days, more if I know its going to happen and cut back usage

Ok, so I live really simple and I am off the grid with a hybrid system of Solar 480 watts with a Honda Generator and a small Wind Generator of 400 watts.
I am pioneering so to speak and solar is rare in my neighborhood so we have to pay for most advice.
I have been learning on my own by trial and error. So far I have been able to survive reasonably well. I live on my own and run a small refrigerator that consumes 150 watts when running, a television at 150 watts, and a laptop computer.

I have a limited budget and have been working this battery bank for one year but would like more storage for night time usage. Am I dreaming or can I do better with the Trojans or something better?

Or would I do better just saving my money? What would be a better way to go with my low end system for a stronger battery bank that would give me longer juice time through the night?