SF Power 1s with Thiel CS 2.3s Enuf Pwr?

I too run Thiels - unless you will be listening at very moderate levels, the Power 1 is simply not enough amp for these speakers (save perhaps the CS.5s). It's not so much an issue of wattage as it is current. Thiels exhibit relatively flat impedence curves, but generally to the low side (4 ohms) and not all that efficiently. The above posts are correct: Thiels do sound best with tube amplification or warmer sounding SS gear. For the 2.3s, I wouldn't use less than the Power 2. Even that may sound strained on occasion with dynamic and complex classical passages. Unfortunately, quality tube current is not inexpensive - either initially or as a maintenance matter. A more cost effective alternative is to run a high current SS amp(s) and the most musical tubed preamp you can afford.

What is the most INEXPENSIVE amp you guy could warmly recommend for the thiel cs 1.5?

By inexpensive I mean under $500 used.

"Power 1 has only 55 Watts but it is a Tube Amp." There is a mistaken idea that tube watts are louder than ss watts. This just isn't true. Furthermore, into low impedance loads like the Thiels, the opposite is more more likely to be the case. I suggest following Thiels guidelines. In my converstaions with Jim Thiel, he suggested doubling the recommended power suggestions when using tubes.
Don't cheap out on amplification when using Thiels.

The bk st-180 has a lot of happy users and can be found pretty cheap. Right now I don't have the budget for a nice cj tube or nice krell. Any other suggestions? I really do appreciate it.

I'm not familiar with the B&K ST-180. If it is like other B&K ST models such as the ST-140, I think you'll find that these amplifiers don't really work that well with speakers that have impedance loads like the Thiels. The B&K M series are much more suitable. Still the Thiels won't deliver all they're capable of without a top quality amp with some real grunt.