Emotiva XPA5 Gen 1

Hi, I am a newbie here and also in the world of music. I started a stere system last month, Just bought a pair of Klipsch R28F and a sub. I only listen to music and now use a Onkyo TX-8555 for Stereo. I would like to have a power amp and use the Onkyo as a Preamplifier. There is a local guy has a Emotiva XPA5 Gen 1 wants to sell it for me for $400. My question is: should I buy it ? Or should I buy 2 channel amp only for stereo music? This gets me to another question: I saw ClassDAudio has A 2 channel amp, 250wpc, for over $500, is it a good amp and should buy it instead of the Emotiva?

Please hepl me! 

Thanks in advance for your help!