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. ?? 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.
Check out the Paradigm x-30 crossover. For that little amount of $$$, try it and see which way sounds the best. (it did nice things taking the low end load off the main speakers AND the amps)
It's pretty much a no brainer.
Good luck!
I'm using a Paradigm X-30 crossover between my Blue Circle BC21 preamp and Bryston 4b which powers my sub. The low-pass setting is variable down to 35Hz. Works for me!
Your c100 and 352's are fully balanced. I would run balanced cables between them and rca's to the sub, out of output 1. I have done just that with my 100 and sometimes I just hit the button on the remote to a/b the sound with,without sub. If you run the signal in and out of the sub you may put a sonic signature on it. Suggestions are fine but always let your ears decide.