Also, you can always proxy in other 15mm figures for some forces if you're not using them for official competition games.
Museum Miniatures have some good one-piece-castings of assorted horse archers (Hun, Mongol, Turk) that look fine as Tartars, they also have some generic cuirassier & ECW cavalry figures that can proxy in for HRI, Danes, or Swedes, plus Dave usually runs a January sale with 25% off.... January is a good time to pick up generic baggage wagons etc.
I also proxied in some Essex 15mm Cossack figures (picked up from Colonel Bill) and a few figures from Alternative Armies.