Lenz Gold Mini with USP power pack so it doesn't stall on the turnout frogs is my best advice. Unfortunately these are expensive $75.00. You are investing a lot into that $15 locot to make it run smooth. You might want to check eBay for some better docksiders like I did. Edit: Just checked. There's nothing worth noting on eBay right now.
Why oh why can't someone like LL or BLI make a docksider with good valve gear detail? These cheap & crude little critters sell like crazy. Oh how I really want a good quality one so I have a pair working the docks in my layout.
Tony's sells them with the super capcitor already attached. It's the Lenz Gold Superpack
http://www.tonystrains.com/products/lenz_decs.htm#
http://www.tonystrains.com/technews/lenz-gold-review.htm
Demo of powerpack with train running over paper instead of rails!
http://www.ruppweb.org/trains/170_over_paper.mpg
It's what I use in mine. (Although I have an older cast one)
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!