Cures for your 18t
steering, you need this:
http://cgi.ebay.com/RC18T-Metal-Serv...QQcmdZViewItem
diffs, go mip and shim them correctly.
bigger motor will help the heating problems.
Mini quake:
Go with the 4700 for your 2s pack, 3600 works better for 3s setup. Either way you will be good, no real need to upgrade to 3s. If possible late you could find a 2500kv motor and run 4s thru the quark 33!!!!
The quake will hold up better than the 18t, you will break the stock knuckles, an upgrade to al, or my tiny screw mod(pics coming) will cure this problem. Other wise just keep the diffs tight, takes about 2mins to do, and you will be ok. I just love the SE models aluminum hopups, they really help the durability of the truck.