Which Amp? Onkyo, Emotiva, Marantz, etc.


My 15 yrs old receiver died recently & I've the opportunity to upgrade. I'm planning to use Oppo BDP-105 in Pre/Pro mode in 5.1 setup.

I'm considering the following similarly priced ($1500-$2000) used/refurbished devices:
Amplifier: Emotiva XPR-5, MARANTZ MM8077, Onkyo PA-MC5500
OR
Receiver: ONKYO TX-NR5010, Onkyo TX-NR3010,YAMAHA RX-A3020, DENON AVR-4520CI & MARANTZ SR7007.

I do understand that the separate Amp would provide better sound & upgrade path but receivers will provide better functionality & features.

Which one would you recommend? I'm open to any other devices than the ones listed above.

Thanks for your time.
hitsofmisses
Thank you all for providing your valuable responses. I built on yours & started digging further. Read tonnes & tonnes of reviews & forum discussions.

First of all, Receiver route is definitely out. I do know that I don't need very High Power. But I anticipate SQ to go up too in high-end Amps.

So, here are the final Amp contenders with my preferences. Let me know if I am going off (I could be after burying myself in my Laptop for the last 3 days) :)
1.) Parasound A 51
1.) Emotiva XPR-5
2.) ATI 2005
2.) Outlaw 7500 or 755
2.) Parasound 5250 or 5125
2.) Theta Digital Intrepid
3.) Anthem MCA-50

Now, it all boils down to what I can get in my budget & in a decent condition.
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Hey guys! I finally bought Parasound Halo A 51 from AudioGon for $2100. Visually there are a few blemishes & it trips-off in Auto 12V setting. My first impression is that it's very heavy (95 lbs) & it gets really hot fast.

Anyway, currently listening to various types of music (stereo, XLR) & movies (5.1, RCA) & comparing notes. In a few scenes, I did hear the background music that I never heard/noticed before but nothing significant while listening to music in stereo. In defense of my previous Kenwood VR-4090 receiver (MSRP 1200/ Used 450) which I was never so attached with, I must admit that though it's 1/4th the price of A51 (MSRP 4500/ Used 2100) it was no slouch in terms of SQ & imaging.

It's almost 24 hrs since I first plugged in. Still exploring & justifying whether my purchase was worth 4 times. Will keep you posted.