Arduino UNO/MEGA + Sensor + Arduino ethernet Shield Rev3 with PoE

Hi folks,
My name is Claudio and this is my first time that I write in this forum.
I don't have experience with Arduino, but I have experience with Electronic sensor and programming. I am a graduate in Computer Science and Automation Engineering.
I need yours help for my first Project with Arduino.
I would like to measure the acceleration & rate of rotation of two bodies using this sensor board. iI want use this kind of sensor

I would like to use either and Arduino Uno or Mega to read the data.
I prefer use the Uno because the board is much smaller and can fit in the experiment easier but mega has more i/o if I need this.
I would also like to use this ethernet card to store the data on its SD card and send it back to a laptop over the ethernet cable.
http://goo.gl/41ReQ

The micro-controller board would need to be able to read 6 other analogue inputs and control 4 PWM outputs.
The data needs to be logged at maybe 100Hz. It doesn't need to be relayed to the network in real time but it would need to be stored on the SD card in real time and copied to the network afterwards.

I saw that the Sensor and the Ethernet Card use the same pin "SDA is on analog pin 4 (DATA LINE)" on Arduino ONE and then
I think it's impossible to use the UNO and i must to use the Arduino MEGA.
And I want Know if it is possible for these devices to do what I'm asking?

thanks a Lot