Is this going to be used only for music playback or home theater? If for music only, I would look at a stereo receiver or integrated amp -- you aren't going to need the features that Marantz offers just for music listening...
I'll take the other side of this issue.
I don't disagree with anything Pearlcorder has said, but there are some counter-arguments to consider.
The economies of scale and popularity of AVR's is such that you get many many more features in an AVR for not much more money. However, these features may be totally worthless to you. I went with an AVR for my stereo system and these are the features that swayed my decision in that direction:
1) Will you use a subwoofer? -
While a typical stereo receiver has a subwoofer output, there is absolutely no bass management - the receiver is sending full range signal to your speakers and full range signal to your subwoofer. If you are running bookshelf speakers, it is nice if you can save them from trying to reproduce below ~80Hz.
The AVR will eliminate the low frequencies from the speakers and the high frequencies from the sub and the rate of rolloff is balanced between the two.
2) Would you like to put a second set of speakers out on the deck or in another room? -
Most AVR's offer a "zone b" feature where you can sacrifice a couple of surround speakers and hook up another pair of speakers. You have separate controls of the source and volume for the second pair of speakers via the remote control.
3) How good are your room acoustics? -
Most AVR's offer an EQ system which measures your room and compensates for peaks and valleys in the frequency response. In a good room this doesn't matter. In a poor room, it will help. In my case I wasn't sure how good my room was, but I knew treatments were out of the picture (WAF), so I played it safe by getting an AVR.
4) How much power do you need? -
Because an AVR is designed to power 5 or 7 speakers simultaneously, if you use it for only 2 channels, you end up with extra dynamic headroom. Does it matter? That depends on the efficiency of your speakers and how loud you listen.
So look at the price difference (I suggest looking at accessories4less for the best prices on Onkyo and Marantz refurbs, but suspect you are already there) and whether the factors above apply to you before you make a decision.