I agree with Most of what Ekobesky said. # 2,3,5, & 6 are spot on. However # 1 & 4 I disagree. I am using a Marantz SR-5005, the bigger brother of your receiver. Our systems are very similar actually. Ive switched from using the internal amplifier on my Marantz to 3 Emotiva UPA-1s. the difference in the sound was night and day! While Ekobesky is right modern receivers have come a long way, you cant match the performance of a separate quality amp. Emotiva and Outlaw (I prefer emotiva by far) have some very nicely priced components and very reasonable prices, wait for the end of the year sales and you can get great deals. Again agreeing with what Ekobesky said, try it in your house. Emotiva offers a in house 30 day trial. I got my amps on Thursday and then had a all weekend movie/music marathon to see if I liked the amps. We did!
Moving on to point 4. The internal DAC in your Marantz. I was using a sony cd transport and a appletv to play my cds and mp3s. I connected them to my Marantz via toslink and digital RCA. This set up did the job. But once I got my Cambridge audio DacMagic it was a vast improvement! My personal suggestion, and this is just from my experience, try adding a quality external DAC to either your CD player or AppleTV. I hear HRT makes a good DAC and Im a fan of my DacMagic, you can get a nice jump in performance for not allot of money.
The once last thing id have to suggest is if you do use toslink use a GLASS toslink cable. Ive never believed in cable voodoo and hype but I was astounded in the difference a short Glass toslink cable can make, I got a half meter Glass toslink via amazon from cables to go for $15.00!!! The vast majority use a plastic fiber but I found them to not be as good and the shorter the better.
I also used Pangea AC-9 2meter cables on the Emotiva amps. I got them used off amazon for $30 each. I would never pay more than that but it did make a difference, the amps sound tighter. Like I said I dont believe in cable hype/voodoo but that was an inexpensive experiment. I guess my over all point with this post is if you wait for a good deal and do a some research you can find very good dollar-to-audible-difference upgrades.
