As for your questions. yes the street series is the exact same as the evo series, the only difference is now you cant change the crystals like you could in the previous two gens. how ever atomicmods has a tutorial on how to change that if you wanted too.

as for upgrades. well you've pretty much maxed your self out on radioshack. Next step is fet upgrades, motors and batterys!

would highly suggest XMDrift for an 2x2 FET stack, RedSXModder for a custom wound to your specs Team Redmade Motor, and a good lithium poly set up. Your cars will be screamers then! and of course me for all yoru future evo series purchases when you get addicted and require more cars bwahaha.

Welcome to the source!