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
Well, I"d stay away from their processors. Also better to get speakers from a company that specializes in them only.
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.
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.