Athena speakers
I started with an Athena bookshelf system and they are pretty good for about $100/pair, but they cant compete with the performance and build quality of the Onix X-LS, Axiom, and Ascend.
It is import that all the speakers tonnaly match, especially the front L/R and center channels. So pick a manufactuer whether it is the Onix X-LS, Yamaha, or Athena and get the matching front and center channels. I bet that if you did an A/B test with the Athenas and the Onix speakers, the Athenas and Yamaha center would be going back.