B&W 805 D4: which 5 channel power amp should I go with (home theater): Parasound or Rotel

I like the Rotel 1585 MKII from your selection options, I use a (2) 1585's in my system with an array of speakers from their 700 series with exceptional results, if for whatever reason you need additional power in a (2) channel setting the Rotel 1590 is also a worthy piece for your consideration, in my case I pair them with a Marantz 8805.   Best of luck to you in your search I hope it works out as well as ours has with whatever choices you end up with !   :  )

I currently use an Ascom 7605 but have also used ATI and was quite happy too.

I listened to both the A51 and Rotel 6 yrs ago.  Both are awesome.  I liked the Parasound better.  More muscle.  If I had to do again I would get the A31 for the front three and a A23 for the back or even the 2125 v 2 new classic for the back.  Unless you are driving big surrounds the A51 is overkill.  My 2 cents.

I have owned several B&W speakers and currently have the 805D4s.  Rotel makes good amos for the money, but the 8 series has impedance dips that Rotel doesn't handle well.  IIRC, the Diamonds (8 ohm nominal) drop to under 4 ohms in the lower treble.  I find that Rotel sounds a bit brittle in the highs driving my B&Ws.  I've used Classe and Pass with better results.  In fact, my 30W Pass pushes them much cleaner at high volume than did my 200W Rotel because it handles the low impedance much better.  Something to consider.  Good luck!

candyisdandy

As above, Classe' is a sonic match as well. 

Happy Listening!