It seems to me you would be way beyond your budget to build up a separate 2-channel music system in addition to a home theatre system. One system can work for both and do a good job.

You have pretty good speakers, but apparently need a better subwoofer (you didn't say which model you have). A better receiver will improve the sound quality you previously had; I recommend either Harman-Kardon or Cambridge Audio for the best sound quality for music listening (as well as movies etc.).

I use the NHT B12D subwoofer, and I think it is one of the best you can buy- $700. Highly recommended. That will give you some of the nicest bass you can get from a sub. It is a sealed acoustic-suspension design, which eliminates a lot of uneven response and resonances common in subs.

Then I would recommend the Harman-Kardon AVR 2650 receiver. IMO it will deliver more power (Harman-Kardon's power ratings are closer to reality than Marantz's) and much better sound than the Marantz 6007, and for a much lower price.

That Marantz 6007 is WAY WAY overpriced and only fair in sound quality IMO. You can get the 2650 for only $520 right now from Amazon and that is a steal. It is very good.

Marantz and Denon are made by the same company on the same production line, from what I have read. They are not the worst, but a long way from being the best.

own room with your own equipment, and if you don't like them, they can be returned within 30 days for a purchase price refund.

Emotiva UMC-200 AV preprocessor is $600 delivered. http://shop.emotiva.com/collections/processors/products/umc200

Emotiva XPA-3 power amp for your fronts and center is $600 delivered. http://shop.emotiva.com/collections/amplifiers/products/xpa3

Emotiva UPA-200 power amp for your surrounds is $349 delivered. http://shop.emotiva.com/collections/amplifiers/products/upa200

A little long in the tooth, but it is a good performer.