Threshold Amp and Sonic Frontiers Pre? HELP

I have a Sonic Frontiers SFL-1 with a Mullard tube and I am considering an amp upgrade to a Threshold S/200 Stasis. I wondering if any of you guys have expirience with SF and Threshold. I've been very happy with a tube pre SS amp combo thus far but I know that a Nelson Pass Amp will give a lot more to my speakers than my BK-ST140.

That being said, I love the BK-ST140. Maybe one of you will convince me to keep it in? I don't know. Any thoughts on that amp with the rest of my system?

I am using a pair of Theil cs1.5 speakers and a Monarchy Audio 18b Delux DAC connected to my computer. I'm using Audioquest Coral IC's and Audioquest Gibraltar speaker cables.

Thanks so much for any thoughts or ideas.
yes! THRESHOLD! I take it you think it's a good idea Unsound?
Keep in mind that the threshold or pass will run much hotter than a b&k and probably won't get quite as loud. Threshold will sound warmer too which may soften up the 1.5's a little. I loved my threshold with my 1.2's-just leave breathing room.
Elevick, the Threshold S200 will actually paly louder than the B&K ST140. The B&K really isn't up to handling the impedance load of those Thiels. Th input impedance will on the Threshold should be a bit better with the SF than the B&K too.
I love warmer... The BK is a pretty warm amp with the MOSFET design but I don't know how it compares to the Threshold. It has more power which will make it play louder, whether I will play it louder or not is another question...maybe. Probably actually. I will step in and defend the st140 slightly in regards to impedance loads. At least with the 1.5's (which are a resistive load and only dip to 3 ohms at most) I have not noticed any problems with the amp. It only gets slightly warm when playing loud and difficult music (Stravinsky's Firebird Suite) and maintains clarity and dignity :). I will say that some of the highs can be a bit brittle when pushed hard but nothing to write home about.
I've owned a B&K ST 140 and ran it with Thiel CS 2's which were a much easier load than the Thiel 1.5's. The B&K ST 140 is not a great match with low impedance loads.
The Threshold is only rated at 5 Watts less per channel than the B&K into 8 Ohms, but below 8 Ohms the Threshold is much more capable. Oh yeah, and IMHO much better sounding.
Those are hard facts indeed Unsound but what does it SOUND like? What do these figures sound like? I want to know what to look for when listening critically. Is that too much to ask? Can words describe such distortions?

as a side note, speaking to B&K the techs told me that they test all there amps down to 2 ohms and make sure they can hold their own. He also said that he was not supposed to tell me that as it was company policy to only state recommendations for 8 ohms.

But the Threshold should sound worlds better! It was 4 times the cost new! I'm excited to say the least. I'm sure you love your threshold that's in your system Unsound.
Esteborino, in the early 1980s I had a Threshold Stasis 200 driving a pair of B&W 801s and I thought that it was the best musical sounding solid state amp that I had heard at the time and I still feel that it would hold it's own from a musical standpoint with amps of today. Unfortunately, I traded it away for a Spectral DMA 200 which I later found did not mate well with my other equipment thus the system did not sound near as musical as it did with the Stasis. The Stasis did not have the transistor sound that typically was associated with amps of that genre. Solid state amps today have improved tremendously in this area.
The Stasis 200 will I think definitely improve the bottom end compared to the B&K. I say go for the Stasis.

The S200 is twice the amp of the 140 on all levels if its in good shape[caps].You can also contact Jon Soderberg for his thoughts.Good luck,Bob
Thanks guys. When inspecting the amp what should I look for to make sure it's in good shape? I'm going to be listening for hums and hisses but should I take the top off? And if so what should I look for?

Thanks so much for all of your help!
How are you connecting the 18B to your computer? Is it a lap top? I am considering the same rig.