what battery to get?

[slow240sx]

I currently got a 2400 rms bass amp and 600rms mids amp. I got 1 deka intimidator agm battery and i can play @ over 13 volts while driving car with stereo on full. I am planning on getting a crescendo bc3500 amp and want to get a new battery. Only want to get 1 battery, so should i get the biggest xs power? Got a cs144 alt to put on in a couple months too. Anybody tried to run this much power with 1 battery and a 200 amp alt? Will b about 4000rms total. I got 3000rms now without too much voltage drop(unless im idling). XSd 3100 is what im thinking. I dont ever play with car off. Did a bass boxing event few weeks ago, voltage was good for 1st 2 rounds but 3rd round it wouldnt stay up. I know this is asking a lot of 1 battery but maybe if i get a good 1 it will get me by. What do you all think?I know most people gonna say i need a few batteries but i feel my current setup does ok for me at 3000rms. Ill only be adding 1000 rms and with putting a better battery in it might take up the difference.

[Monergist]

I'd say a D3100 from XS Power and a 270 amp alternator from Mechman or DC Power will do the job.