You don't have to go brushless, picking up 2nd hand modified or even stock motors can give you quite a cheap boost in speed.
Brushless and lipo will give you the most speed with minimal maintenance though.
There's combo systems out there a few people have the losi system I'm not sure if they have a lipo cut off, I should imagine they do.
http://www.modelsport.co.uk/?CallFun...n&ItemID=30214
You'll want a 2s lipo, you might be able to pick one up 2nd hand for a reasonable price from the for sale section on here but you will need a lipo compatible charger, trying to charge it on your current charger will definitely end in tears.
The tamiya connectors are poor and will be a fire hazard if you try and run too much power through them. The 4mm bullet connectors are pretty much standard use and can be picked up very cheaply from ebay, i've bought some from this seller and I've not had any issues
http://cgi.ebay.co.uk/20xSET-4mm-GOL...item2a05323610
I'm not familiar with the model you've got but have you built it with ballraces/bearings in? If not this is the 1st thing that you need to upgrade, pushing extra power through the car with these in will end up with melted parts.