2S lipos are 7.4v AMPs don't really matter except for run time.
6cell NiMh's are 7.2v so pretty much lipos can be used in anything that takes NiMh. But with brushed motors you need a Low-Voltage Monitor to monitor the Lipos charge and tell you when to stop. (Low Voltage Cutoffs do NOT work with XL-5 ESC's that are in traxxas vehicles)

If your going to run it near a forest you will want a 4wd seeing 2wd's kinda suck in grassy locations.
Theres the E-savage for around $350, its 1/10th scale
http://www3.towerhobbies.com/cgi-bin...&I=LXTDD6&P=ML http://www3.towerhobbies.com/cgi-bin...&I=LXPCH5&P=ML (No idea whats different about the 2 cept ones cheaper and out of stock)
or the Savage Flux its 1/8th scale
http://www3.towerhobbies.com/cgi-bin...=LXWLZ8**&P=ML

Then theres also the Revo from Traxxas that has a very loyal following
http://www3.towerhobbies.com/cgi-bin...=LXUYD6**&P=ML Brushed
http://www3.towerhobbies.com/cgi-bin...=LXWGD0**&P=ML Brushless motor