I'm also a DIY, but I've been operating an active 2 sump pit system for around 7 years without a flood. I recently replaced one pump (second replacement of this pump) with a Zoeller M53. Unless you've got an extreme amount of water flowing in a storm the M53 should be more than adequate at 43gpm.
I got my Zoeller at JH Larson (not Thompson as I mistakenly wrote originally) for around $120, they have locations in Wisconsin and are super nice. Also got some Zoeller check valves for $8. You need a check valve if there is not one on the pump already. The instructions tell you, with the M53 and Watchdog backups you need to add check valves. Also drill the anti airlock holes for these pumps per instructions.
Put the valves close to the pump, but above the cover is ok and I prefer this for ease of installation and keeping the pipes clean under the cover.
The switch on any pump is the weak link so you may want to have a decent extra switch you can add at some point if/when the pump switch fails. That's when clean pipes come in handy for securing an after market switch.
Watchdog is not a Cadillac system, but it's also not a junky Yugo. Maybe think of as a Chevy. The Special is very reasonable cost with a decent flow rate and good battery. The Big Dog is better but about twice the price.
I've been happy with the Special. Regardless of what you spend or choose, if your system is active, proper maintenance and periodic monitoring is the key. Make sure the back up works by testing every now and then. The pricier ones do this automatically, the Special you need to push the button which is very simple.