Let me start by saying the Marantz AV7005 is currently class B rated in the new edition of Stereophile. I don't think you will be unhappy, but I do think you could do better two channel for the money. I'm currently running a Marantz SR7005 as a preamp, with a Parasound A23 amp connected to my B&W 804d's. I like the sound I get, but I think the Marantz is a weaker part of the system. Don't get me wrong, it's great for AV needs and the built in DAC works well, but the unit is a jack of all trades and master of none. Plus you already have an outboard DAC.
I'm sure your AV7005 would out perform my SR7005 due to the balanced connections and additional component isolation, but I still think you can do better for the money. Especially on the amp side.
I would suggest taking a look at the Parasound P3/a23 combo, which would be in your range, or if you can find a good deal on a-gon, try and find a used Ayre AX-7e, which is Stereophile class A rated. It would also be worth your time to visit a non-Best Buy B&W dealer to hear their recommendation if you haven't already done so.
Regardless of the system you choose, happy listening.