Choice of geared motors

I was wondering what motors to use for my school project. its going to be a 4wd rover (skid steering) with a robotic arm and wireless camera. i have a chasis welded up and ti weighs only 800grams. Max target weight of the whole system including batteries is 4kg. 

i am willing to spend a maximum of $40 on them.

The problem is choice of motors. i found these geared motors. i found a seller who sells then in packs of 2. each one of them has a stall torque of 4kgcm and the max rpm speed is 300.

http://www.ebay.com.au/itm/2X-12V-300RPM-Gear-Box-Motors-Cars-Boats-Robots-New-/120783134079?pt=LH_DefaultDomain_0&hash=item1c1f3c5d7f

 

and this type
 http://robokits.co.in/shop/index.php?main_page=product_info&cPath=2&products_id=49&zenid=76798c37fec40f309c2ae51f26c8464a

and this type
 http://robokits.co.in/shop/index.php?main_page=product_info&cPath=2&products_id=248

the building starts in two weeks. so please help. thank you.

 

I would go with the ebay

I would go with the ebay ones because i know projects done with them and they are really pulling your pants off…metal gear and reliable.

Thanks

i just remembered that one of my friends bought two for his custom made rock crawler. i am going to ask him if they have good torque