SS amp for B&W 801ms2 Emotiva XPA1 or W4S SX100

Go with the Bryston.

I use a w4s st 1000 to drive my mag 20.7's beautifully

I have a pair of Emotiva XPA-1's that I just picked up used from a good friend of mine who is a long-time audiophile, especially 2-channel.  

I like them a lot.

My gear:  I own a Music Hall MMF9.1 w/the Roy Hall recommended Goldring Eroica LX cart fed into a Budgie SUT...I have an Audible Illusions Modulus II which is fully modified with upgraded caps and wiring, and speakers are Mirage M5,M5si,M3si (two pairs) and a pair of GoldenEar Triton Ones...I also have an Oppo BDP103 and a QNAP NAS running TwonkyMedia for digital sources.  Interconnects are all home-built Canare 4S11/L4E6S.  I also have Pioneer Elite SC89, which quite frankly, I was (and still am) very happy with.  

On to the Emos:  In my system, they sound quite good.  The Triton Ones are very efficient due to their integrated 1600 watt sub sections, so for two channel I put he XPA's into Class A mode and that makes them very sweet and smooth.  They have plenty of power to drive my Mirage M3si's and give them a solid, deep and tight bass bottom end, tight mid-range and smooth highs that my Pioneer could not stack up against.  I was considering picking up a Bryston, Anthem or Parasound amp prior to picking up the Emos, and I might still do it to satisfy my curiosities as I am building three separate systems (bedroom 2 channel, living room 9.2 and dedicated basement home theater).

I will state this about the Emos:  Even if I pick up some other gear, I plan to keep these Emos long term.  They are built very solid, sound good, have plenty of power, and their customer service - as I understand it - is very good.  They are also assembled in Tennessee by American workers.  I can't imagine you would not like them.  I can't hear any audible noise in my rig (dedicated 20 amp circuits for my system) and they handle everything I can throw at them from Vintage Pepper Adams to Shaggy. Transients are very fast and tight, dynamics are great and the bottom end they support is magnificent., and they allow both my M3si's and Triton Ones to reveal the smooth highs that each speaker's tweeter design is famous for.

Are there better amps out there?  Sure.  Does the price difference translate directly into performance?  It should, and most reviews say it does, but if looking for a great bang for buck, they are a solid purchase.

@dimora - I agree on the Emotivas. They are very nice amps for the money. The XPA-1 amps are a bit too much in the high frequencies (a little bit too bright and harsh) and running them in Class A mode definitely helps with this. You could also replace the stock fuses with Isoclean fuses to further help with the brightness/harshness. The Isoclean also gives a slightly warmer sound. The XPA-1 uses two 10amp 5x20mm -- accessible by taking off the small square panel on the bottom of the amp (only take out the screws on the outside part of the square panel - the inside screws actually hold the circuit board). It also uses two 1amp 5x20mm on the input pre-driver board - just take off the top part of the case/cover and you can get to them directly.  Or you could try Furutech fuses if you don't like a warmer sound.

I have an Emotiva ERC-3 cd player and CMX-2 power filter. While I have no experience with their amps I could vouch for their overall quality and even more so their outstanding value. I've never needed their customer service but have called with questions and they are responsive, knowledgeable, etc. so my gut tells me there is a true company that stands behind their product.

As you've asked for other suggestions perhaps you could also consider a Musical Fidelity M3si. That too should be in the 2k price range.