Hi! Go with used audio research VT100- MKii
$2500 tube amp?
Look for some Dodd 120 MK II monos and throw in some Winged C EL 34 output tubes from Antique Electronic Supply for another $100 or so ($17 ea matched), and you'll have money left over. if you can also get the Dodds with the platinum cap upgrade, so much the better.
Thorman's nod to the Thor line stage preamp is a really good idea too if the money is in place. I have one too, suppliying my Dodds. I'd almost guarantee you won't be disappointed. I too listen to mostly jazz and blues... bluegrass and so forth.
They'll drive many, many speakers very well. Even my 87db Phase techs which drop to 2 ohms.
You might even wind up with $$$ left over.
Have you considered the The CARY CAD 120S Power Amplifier recently named 2008 Product of the Year from Electronic House magazine and a STEREOPHILE 2008 Class A tube amp.
This stereo power amplifier is rated at 60 watts per channel in triode mode and 120 watts per channel in ultralinear mode into an 8 ohm speaker load.
The output stage may be switched on the fly from triode mode to ultralinear mode by using a front panel selector button. The power supply features 1,120 micro farads of capacitance for ample reserves in demanding usages.
CARY is a great company and has a great customer service department and I'm sure they will be happy to answer any questions you have. While the retail is $5,500, there are some great deals right now on Audiogon withinn your range.
If you chose the Sonus Faber for its warm sound, be aware that the Audio Research gear tends toward the opposite side of the tube scale. If you find the sonus sound too lush, it may balance it toward neutral. Just for my preferences, it could be a little like water and oil. I like the former suggestion of a Thor linestage and I'd like to add the Dehavilland Mercury to your list. Good luck, Jeff
My older Phase Tech PC 10.5s 3 way towers (mentioned above) are now in a room comprable to your dimensions. The dodds are never taxed and the vol on my Thor pre never gets past 10 - 10:30 AM ... usually it's around 9AM or less.
Your's are more efficient, and have an easier impedance load. 88db at 6 ohms should be tube friendly enough in that size room, so unless you go way low on power, like say under 20wpc, you ought to be fine. A BAT vk60 drove them pretty well in a 14x21x8.5 room... though bass was an issue there. They start rolling off at around 40hz, but in a smaller room eg., 10x11x8.2, the bass is fine. Sufficient in fact.
80% of the music is made in the first 20wpc.... so I hate to say just how much one needs on tap from any amp... I feel the considerations are too numerous, largely depending upon how loud you listen routinely, for example. How much head room is also a thought. Power reserves are a definite good thing, as much if not more so than is the power output itself. it's doubtful any of us will actually use ever ounce of abaiable power on tap achieving a prefered volume level, if even a moderate choice of amps is made. The main concern past power reserves, headroom, is certain freqs require more power to reproduce as the amp is taxed more... as the vol being turned up.
Power ratings of amps to the sensitivity and imp of the speaker alone isn't how I'd approach it. you, and the room play a big part too.
Given a speaker with 88db sensitivity, needs 1 watt to develop 88db SPL at 1M on axis, on paper it should only take 8 watts to develop 88db at a 4M distance which exceeds one of your dimensions. Consequently at closer range the SPL will have increased. Again... ON PAPER... and on axis or right in front of the speakers drivers (vertically and horizontally).
There are other considerations. I'd stay in the 50-60 wpc min power camp in that room with those speakers to be safe. Especially if rock is the main genre being tuned in regularly, and you listen at or above 93-94 db... which is pretty dog gone loud actually, if on avg. IMO.
true too is the note on matching the sonics of the amp to those of the speakers, as was already said. too much of a good thing, is too much.
Art audio makes some very good amps though I've not tried them meself. I understand they are suprising given their rated outputs. The Cary V12 is a good thought too. but it uses four more EL34 tubes than do the Dodd monos put together. the BAT vk60 uses eight 6sn7 input/driver tubes + 4 russian output tubes... more tubes means more $$$ when ya wanna roll in some different ones just to see what happens.
Good luck with your choice (s).