perhaps look in the second hand section and buy a recognised name (lrp/nosram/tekin/novak) then you will get a product that people will be able to help you with as they have more knowledge on those products.
motor wise dan has already said about and if you are running a 15x3 now then a 8.5 will be more than enough for you.
when considering lipos then look at the c rating and mha rating as well. the higher both of these numbers are then the more grunt your car will have. hence most people using a 7.5/6.5 motor in 2wd at a national level but then using monster lipos to get the horsepower they need. with the 8.5 motor perhaps go for a 25c rated 4000-5000 mha lipo so it remains smooth and easy to drive like your current package. motors again use the names mentioned above, they are used by a lot of racers so will be in good supply second hand if needed.
for lipos look at trackpower/orion/vampire (there are loads of makes available). ive tried to remain unbiased to what i feel is best as they are all much of a muchness. some warrentees are better than others on the speedos so make sure that what ever you buy has a good one
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Nathan Ralls HPI, Custom Blitz,
www.piraterc.com mr-o foams
woop woop racing officialy keeping team toe out inline
