You are correct, you will need the ir-543 and just one switch to start, I am the type to go for quality, the features, looks, and reliablity of good switch's are worth the extra money to me. PCS and Smarthome are both excellant brands of switch's. I do my shopping here
http://www.homeautomationnet.com Bill the owner is wonderful to deal with and has good prices as well. You have to decide for yourself where to draw the price/quality line.
Bill also has a nice PCS starter kit at a good deal.