Is Nelson's pre as good as his amp ?

Just wonder is it worth to replace my arc ls-3 with aleph p ? This wonder is based on very satisfied experience with aleph amp (first 5 then 2). OTOH, one stereophile's reviewer seemed to prefer AI M-3. Any thought ?
I have had the Pass X2.5 preamp for five months, initially into the Aleph 5 with balanced interconnects and now into the GamuT D-100 Mk. III. This is a wonderful fully balanced SS preamp. It is very quiet, with excellent clarity, smooth, great sound stage and all the other attributes of a great preamp. I think it is near world class at a value price. TAS rates the Pass X1 very highly which I've been told sounds very similar to the X2.5. These preamps are the next generation after the Aleph-P. Ultra Audio reviewed Pass X2.5 on feb. 15, 2003 and compared it with a 14K Rowland design and it was fairly close. Nelson has plenty of info on his preamp at his web site.
Don't feel sorry. I couldn't remember all the details either. I actually just pulled out the manual to refresh my memory...

I think Pass would recommend to use balanced for his amps, if the balanced input is equipped. You can drop any questions to Mr. Nelson Pass and he will answer your questions. Excellent customer service!
Any one know what is the hardware and sound difference between v1.0 and v.1.7 in addition to the spec in service manual? Thanks !