Cambridge DacMagic & Oppo Blu Ray - Other Question

I just picked up a Cambridge DacMagic over the weekend, based on great reviews and a fantastic value. I figured I could integrate it in one of my systems. I am going to experiment with it in my dedicated AV/HT room. I have a couple of questions on the DAC (Settings, integration, and compatibility). The main equipment in the room includes:

Integra 9.8 Processor
ATI 3007 7 channel amp (300 Watts)
Pioneer Elite 60" Plasma
Usher BE 718's (front & rears)
New Usher BE 616 Center Channel
Arcam DV 137 Multi-use
I am getting the new Oppo BDP 83 Blu Ray on Wed

I hooked up the Cambridge DacMagic up to my Arcam DV 137 to test it. I think it made a small but noticable difference in CD listening. For those with this DAC, which filter do you find has the warmest sound, (Linear, Minimum, or Steep Phase)? I think only using it for a couple of hours, the minimum phase filter is the best setting, other opinions?

I also have some questions about the connections to and from the DacMagic? I am testing two different digital input connections, an Analysis Plus Oval One Digital Cable and a WireWorld optical cable. I can't tell a difference in sound, any opinions on the digital connection?

Another question on the output connection to my processor. I am currently running a set of Analysis Plus Oval 3 RCA (unbalanced). Would I pick up much improved sonics by using a set of balanced cables instead, or is it splitting hairs?

Last question, on anyone that has the new Oppo Blu Ray player. I am planning on trying the DacMagic on the BDP 83 for 2 channel audio (CD's). Has anyone tried an ouboard DAC on the new Oppo Blu Ray player, any appreciable improvement or are the DAC's really good in the Oppo?

I am not sure if I am going to keep the Arcam DV 137 after I set up the Oppo Blu Ray. Anyone compare the audio from your good DVD/SACD players to the new Oppo player, specifically audio quality (SACD, DVD-A, CD's)?

I would appreciate your opinion?

Thanks