My initial thought was to purchase only the RSP1a. I opted however to spend the extra money and purchased the RSPplay Duo and boy was I glad I did. Especially now since discovering the MFJ-1708sdr RF switch. I'm quickly seeing the advantages of having two waterfalls working simultaneously on 40 and 20 meters. Talk about a game changer when it comes to contesting. For the money, the RSPPlay Duo is well worth it. You won't regret purchasing one. I'm really hoping to get my general class soon so I myself can take advantage of my RSPplay Duo's full potential.