I put an Interstate in mine. There is a fair amount of leeway in the mounting brackets. Honestly very easy to do yourself. The Interstate was smaller than the OEM, 100 more CCA. Great battery. I doubt you'll ever use the warranty whether 2 or 3 years.
I owned and operated an independent automotive parts store from 1982 to 1996. Having stocked and sold many brands of batteries. To me, Interstate batteries are by far, the finest battery made.I have a 2013 1.6 MT with 58,585 miles on it. Went in for one of my (lifetime) free oil changes today. They said my battery was showing 210 CC amps of the original 500 CC, and offered to put one in while I was there for $159.
I decided to wait on their recommendation, and stopped at a few auto parts stores on the way home. The AutoZone guy came out and tested my battery (which as he pointed out, only lists 410 CC amps, NOT the 500 my dealer said it had. His test showed me at 290 of the 410 I was supposed to have. He also thought the $159 was a good price.
When I did a search for Kia Soul Batteries, an old thread from this forum was part of the results. There, I read all about the minor differences in size between the EverStart Maxx 121R vs. the 124R. Some saying the 124R was a better fit, etc.
I figured I would opt for letting my dealer sell me a battery (after all, it has now been nearly 7 years of free oil changes), but when I called the dealership back, I discovered that the battery they use is made by Interstate, but that it only had a 2 year warranty.
So after hearing that, I figured maybe I should just go to Walmart and pick up the Everstart Maxx for $119.76 . . . since that battery comes with a 3 year over the counter replacement. I know it would be convenient to have my Kia guys install it, but I think it is something I can do in 20 minutes. (The Walmart Automotive bays are closed here in Ohio.)
Am I missing something here??