I am looking to put together a new HT/ 2ch. system and need some help in selction of the right CD player. I want to get the best possible player, but do not want to buy something that is more than I need based on the rest of the system. I have not bought anything yet, but this is what I expect to have for a basic setup:

Marantz SR7200 or Onkyo TXSR605 HT receiver
Paradigm Atoms or PSB Alpha B1 or KEF IQ3 or B&W 685 speakers (with a sub)

A couple of the CDP I am looking at include:
Marantz 5001, Oppo 980H (combo unit)

My questions:

1) Is the Oppo unit much of an improvement vs. the receiver DAC? In which case I could use digital or analog connection.

2) Is a higher end model such as the Marantz 5001 a significant improvement over the receiver DAC? In which case I use a analog connection.

3) Does it even matter given the fact that this system is lower end anyhow?

What would be recommended for this level of a system for the CDP? I woudl prefer not to spend the money for the 5001, but will if it seems that is the best route to go. If the differences are negligible, I will probably just get the Oppo.

Thanks in advance.