David,
Man, this is strange that you bring this subject up. I've been seriously thinking about starting a series of articles over at EnjoyTheMusic on this
exact subject. Do to a major highway shut down in St Louis, I've begun tele-commuting about 50% of the time at my real job. In turn, I took my old 'Grape Room' and converted it onto a home office. The room dimensions are 9x11, nearly the same as yours.
Here are some (not so spiffy) pics of the room to give you an idea of what I did.
The Headwall

The Backwall

(sorry about the fuzzy pics, I haven't done a formal 'shoot' yet)
Like you, I'm doing this room with ZERO treatments. Not because I don't want to, I simply can't without overwhelming the room and making it look too cramped.
I'm using the Odyssey Epiphany's as speakers. They have great off axis dispersion and imaging. You are going to
need that as you will definitely loose your sweet spot in an office configuration. The amp pictured is the Primaluna Prologue II. It's really too much amp for the room. Previously I had the little factory modified JoLida 102b in here. It was super sweet with ample wattage at 25wpc. Next up in the room is the Opera Cyber 10 Multifunction KT88 SET.
Now, sources. Well, I thought about doing my SB with a DAC but honestly, I thought why? Since my computer is in the same room, I could feed a USB DAC (or in the case of the Opera Cyber 10, it has an onboard USB DAC). I've started playing with the Trends 10.1 and the MHDT DAC's and also the DAC 707 Super Pro (see pic below). Using Foobar/ASIO as the music player and feeding these combo's, I'm getting some
damned fine sounds. Nearly as good as when the room was set up as a dedicated listening room. Sure, I've lost some of the depth of stage and that perfect placement of the performers but I still get a very reasonable soundstage with OK placement.
The single biggest issue here is that I want....no need my music. In all my years working, I've always had music playing in the background, regardless of where I was. If I couldn't have a minisystem, I used headphones (anybody remember the Bone-Phones from the Home Shopping Network circa 1985?).
The other great thing about Foobar is it has a built in EQ (yes I said EQ.....RUN FOR COVER!). The great thing about this EQ is it is all done in the digital domain. It allows you to trim back some of the bass buildups you
will experience from sitting in a node in an untreated room.
When it comes to amps, think small wattage. With 86db speakers and sitting nearfield, I doubt seriously I even use more than 5 or 8 watts (I sit 5' from the closest speaker).
I know you may not want to consider this but give it a thought or two. Why not sell your SB and AN DAC? Reason I say this is, like the Cyber 10 (and a growing number of others), I personally think that more and more amps will be offered with onboard USB DAC's. Lets face it, what you are thinking about and what I've done is going to be the future of audio. Not to mention, it is a lifestyle thing for many, many people. They will want a completely integrated amp that interfaces with their computer (used as a music server). They may tolerate a small external DAC like that little 70 Super DAC (which sounds pretty damned good for $110 BTW).
DAC707 Super Pro USBLots to think about. Bottom line is you can downsize, do it in a small room, without sacrificing good sound.
Here is a link to the little Opera Cyber10 I wrote a few months back.
Cyber 10 Article