charrison:

I've been fighting a wet basement for 20 years. Most years I win,
some I don't. (Recently had a couple feet of snow followed shortly by
an 80 degree day.)

A couple of inches of heavy clay soil will really help.

I like the idea of a second pump rather than one bigger system. The
advice to check out the system when it is operating is also good. It
may not be installed very well and your pumped water may be
returning. My system pumps to a pipe that goes 20 feet away and a
foot down.

The floor in my basement is the old fashioned thick vinyl 12" tiles
put down with mastic. It has held up well to the occasional flood for
many years. Read the fine print and make sure it is guaranteed for
sub grade installation. Most of the thin self stick tiles are not. We
use area rugs that can be rolled up and moved in an emergency.

You may also want to leave a gap at the floor in the wallboard of a
couple of inches. Cover it with an oversized baseboard that stands up
to water. Just in case.

Good luck.

dss