The cheapest way is to buy IR turrets from Erik for the two Taigen tanks, but the pershing is a problem. They don't make that tank in IR so you have no factory set up to fall back on. Changing all three tanks to another complete system will cost more than buying a cheap Panzer III from Taigen or HL and converting the Taigens to IR. Probably your lowest cost way to go will be IR turrets for the two TG tanks, and the mako for the M26. The mako will play with any system out there, but keep in mind that all this only gets you the HL/TG style IR battling, with squirmy track movement and only about 30 feet of range (on the taigens, the M26 will do better on the mako). Anything more will cost more. As we musclecar guys say, "Speed costs money, how fast do you want to go?" and "The top speed of a musclecar is directly proportional to the depth of the owners wallet". You are now faced with a very similar situation.