I was wondering if you all could give me a hand.

I have a Mongoose XR200 (yeah its a cheap bike but I am no means hard core and the bike supports my needs and my wallet) with a broken rear derailler. While doing some moderate trail riding, I came down on a log and pushed the derailler into the spokes which in turn pretty much destroyed it.

I have been trying to research all I could to try and get a replacement. With the information I have, I have come to believe that the derailler that came equiped was a Shimano RD-TX50 as seen in the following link
http://www.amazon.com/Shimano-RD-TX5...509993-1767212

The question I have is should I try and get an upgrade or go with another TX-50? Is the TX-70 a better choice? Anyone out there have an XR200 and think I have my derailler model number messed up? I appreciate any help you can give.