RCA to XLR? Do I need to do this?

Hello All,
I am a newbie to the Audiophile stereo world and I have a home system that is for both Stereo listening and Surround sound home theater.  I have a pair of Sonus Faber Venere Signature speakers running from a Mrantz SR6012 Receiver.  I just ordered a Krell KAV 2250 amplifier to finally get some power to these speakers.  
My Question:

• Should I use an RCA to XLR interconnect cable (Marantz signal is not balanced) or just use a good RCA to RCA (the amp offers both inputs)
  
• Which cables would you recommend for a 6' run and on a conservative budget?  Maybe up to $200 per cable.