Alan,
Actually, I would caution the use of X250 and recommend going with the X250.5. Prior to my current speakers, Verity Parsifal Encore, I had the Thiel 2.2 and then 3.6 for many years. I was driving the 3.6 with a Mark Levinson 333. When it died, I replaced it with a Pass X350.5. I had been thinking about replacing the Thiels for a while at that time, but the Pass 350.5 brought new revelations about the Thiel 3.6 that I had never heard before. And I was sure that I had pushed them to the limit with my previous setup. It made me reconsider keeping the Thiels for few more years.
Few months before I purchased mine, I had a privilege to listen to a side-by-side comparison of X-350 and X-350.5 at a friend's house driving a pair of Avalons. The X-350 sounded like a typical SS that people complained about, cold, sterile, and unimvolving. We were all surprised that it was very out of character of what we wouldexpect from Nelson Pass. But the X-350.5 was very different. It retained all the good stuff of the X-350, but brought back the midrange warmth that Pass was famous for. We all felt the difference warranted more than a ".5" upgrade designation.
FrankC