My initial advice is stick with what you got. If ~$100 is that big of a deal, wait and save up more money. Even the $97 D3 kit you speak of (which if it's the one on eBay, isn't Sakura brand, it's a knock off) requires some extra little parts and work/tuning to really perform well. It's worth the money from what I've heard if you do the necessary work.
New D3 or D4 is probably the cheapest, effective option, all things considered. That or a base spec MST.
As far as batteries go...LiPo are really what you want for drifting. I initially started with traditional NIMH as that's what I was accustomed to, but after going with LiPo, the performance (consistent power and quick initial punch to start drift) and weight savings really made a huge positive effect for me.