Crossover needed for subwoofers, or not?

Need advice on whether to use a crossover system after the preamp to shunt the low frequencies to the subwoofers.

Or, can I just run the full audio spectrum to my two amps and then to the speakers (35hz low frequency limit)...and use the RCA outputs from the preamp to the subs? (The subs are "adjustable" at each sub's filter frequency/volume controls.) And adjust the filter to only amplify below 35Hz.

Pro and Con:

One way, I avoid the complications of a crossover network and extra interconnect cables, but am worried about feeding all those really low frequency lows to the 10" woofers of the speakers, muddying the sound.

The other way, I have more cables and another electronic piece of equipment in line, but those lows ALL go to those two 400w subwoofers, keeping the midrange cleaner. ?? ...as I can set the crossover frequency to?.... 75Hz?

Opinions and advice appreciated, Thanks.

My system:

McIntosh C-100 preamp
McIntosh MC-352 ss amplifiers
Tannoy Definition D-700 speakers

System is bi-wired and vertically amped, with each speaker of the Tannoy having its own 300w channel by running the amps in stereo mode.

2 M&K V1-B 400w subwoofers wired for "stereo" R/L channels.