If you set on spending that much then just get two 6VDC GC2s with twice the storage capacity and true deep cycle and never worry about if you have enough power.
When comparing us the 20 amp hour rate number listed. Two 6VDC will get you 215 while the single 12VDC only has 110. There's a little more to it but the 20 amp hour rate is a reasonable comparison number.
More info -
https://www.batterystuff.com/kb/arti...ate-mean-.html