Yes, Halo is Parasound's top of the line series. The JC1 is the flagship power amp, the A21,31,51 are the more affordable ones but still highly regardes as smooth and sweet sounding. I suggested this brand initially because you said you were in Taiwan so I thought you may be able to get decent price thinking for something that is made locally. Now that you mentioned "strings", the Halo amps being known for their smoothness, should be a great choice for you. I am planning on getting one shortly myself, any day now.

If you want multichannel, talk to Rich about the A51 (5 channels), he will tell you how happy he is with it. The A51 will provide your speakers with 400W of clean power. In that case you can sell the RDA. If you need two more channel, you can just pick up a low cost two channel Onkyo or something else for the rear channels.
Objectively though, most good quality amps shouldn't sound all that different, so that's why I also mentioned the option of a better sub. You may be amaze how much a high end sub can do for you, yes even for two channel critical music listening. I do believe most speakers would sound better if relieved the duty of producing much below 80 Hz regardless. However, some people, you are probably one of those, really believe in how a good amp can make significant improvements and in that case you can't beat the Halo at their price point.