Filtration for 125 G tank help needed...

Dead spots are not as important in FW tanks. If you have two filters on either side of tank, I would not be overly concerned.
 
Most bang for the buck on large tanks is still the wet/dry sump filter. I have a 30g 650gph sump and a Filstar XP3 on my 125. The XP3 is set up with only sponges for extra mechanical. Though it is a birchir tank and not really planted (some anubias here and there).
 
I'm running a C-360 as my main filtration with a chinese knock off of the C-360 as secondary. I really am a fan of the two filter setup as it really adds a level of security. If one of the filters stop for some reason. Given my travel schedule this is very important as I'm commonly away for a week or more at a time (I spent last week in Brazil).

It also greatly increases the time between filter maintenance. I'm on a twice yearly schedule now with my 125 gallon planted tank.
 
As others mentioned, 2 filters for sure.

I personally would go with 2x rena filstar xp3 or xp4 (you can never overfilter!), or you could do a canister and hob combo. My 55 gal has an aquaclear 110 and a rena xp4 on it (see, you can never over filter...... Lol).
 
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