California98Civic,
If you get the Odyssey PC1200 battery it won't be supported by their 6A charger that you have. Their chargers page indicates you need at least the 25A charger.
ODYSSEY Batteries - Chargers I spoke with Kathy at Odyssey several times; their batteries "like" higher amps and also a bit higher voltage than standard lead acid. You might be willing to wait for a charge to complete but the battery won't do as well, long term.
I really suggest you avoid lead acid and look into a LiFePO4 battery similar to what I got. The main reason is that with lead acid, you can only use 20% of the capacity if you don't want a short lifespan (for the battery). That turns a nice 50 AH battery into a not so nice 10AH battery.
With lithium, you can use 80% of capacity and still have about 2000 charge/discharge cycles. More if you discharge it less than that. So my 40AH battery can serve as a 32AH battery and that's pretty decent.
The only caution on that is that it's my Lithium's output is limited to 100A by the "PCM", protection circuit module. It might not be enough to power the starter. The 100A limit is just for battery protection. You do need the PCM if you don't have a full blown Battery Management System, to keep the cells balanced. Again, that's for longer battery lifespan. I got around the 100A limit by keeping the main old lead acid battery in the circuit, wired to the charger. Or you could have a bypass jumper going straight to the battery, eliminating the PCM. The PCM would still function normally but would let the starter have the juice it needs. The pack I got will actually handle 400A load, and even more short-term.
Good luck with it all,
Bruce