Desperately Need help with RC Sumo bot

[rippa911]

I started another topic because for some reason I can't edit my old topic..

HI there. I'm new to robotics. I started research for a RC controlled sumo bot a while ago and I'm having lots of questions.
 I live in a third world country and its really hard to get components and stuff.
So I've decided to compete in a state level RC controlled robot sumo competition.
I've decided not to use a microcontroller to keep the cost down and its not really required (amirite?)
Anyways here are the rules:

Objective

To design and build a robot which pushes another robot off from the round table of diameter 1.5 m. The robot can only push other robot by contact and not by impact.

Machine Specifications

1. The Robot should fit within a dimension of 20 cms by 20 cms by 20 cms.
2. The maximum weight of the robot should be within 2.5 kg.
3. The robot should be controlled by a wireless remote.
4. Principles of capacitance and magnetism are to be avoided.
While designing the robot, flames, smoke or any liquid or chemical cannot be used as defensive mechanisms
5. The maximum volts at any point should not cross 12v.
6. No external power supply is allowed
7. A description of machine should be sent and verified before building to xxx This e-mail address is being protected from spambots. You need JavaScript enabled to view it before xxxx.
8. The Robot cannot fly in air.


Judging Criteria

1. Time required to defeat the other robot
2. Design
3. Cost

So here are my question

Open questions:

Should I go with 2 wheeler or a 4 Wheeler?
DC geared motor or Stepper motor?
HOw much torque do I need?
What should be the optimal wheel diameter?

[Razor Concepts]

Two wheel design using servo motors and a standard hobby-grade RC transmitter and receiver will be the cheapest option (TX and RX can be purchased used online for about $20).

Using a DC geared motor or stepper motor will require a motor controller, adding more cost.

[rippa911]

Two wheel design using servo motors and a standard hobby-grade RC transmitter and receiver will be the cheapest option (TX and RX can be purchased used online for about $20).

Using a DC geared motor or stepper motor will require a motor controller, adding more cost.

Are you sure servos can sustain robot's own weight 2.5kg and push another 2.5kg of opponent's weight? I doubt that since they are not heavy duty and have less torque..
How much do motor controllers cost?
Is a costly motor controller required or the cheap ones will do fine?
Can I create my own motor controller using L298s or something similar?
Which one of the below will you recommend if you have to?
http://robokits.co.in/shop/index.php?main_page=index&cPath=1
http://www.nex-robotics.com/products/motor-controllers-3.html
(1USD=50 Rupees INR)

[SmAsH]

you would be surprised how much torque some servos have.

[Razor Concepts]

If you want to use a motor driver like 298 you must have a microcontroller and other supported parts, greatly adding in costs. If you use servo all you have to do is plug it in the RC receiver, no extra circuitry required.