mppt vs pwm

Can you point me to some cheaper model controller that would allow these 24V panels while keeping a 12V battery bank? A 60A Tristar just sold on eBay for under $500 but I'm not ready for that kind of financial commitment. I'll be able to draw off half a bank with the inverter for testing till I find something. I know this not ideal, but I can bank switch until I get this right.